Wongnai POS / Ocha Integration: Unify Sales and Guest Data, End Cashier Double-Entry

1. Count the loss as mismatch plus invisible LTV, not as typing seconds

Sukhumvit and Phrom Phong izakaya, yakiniku, and kaiseki rooms of 28 to 40 seats keep the booking book of record in a LINE Official Account plus paper or an iPad grid. The payment book of record is Wongnai POS or Ocha. Friday 19:00, the host confirms “T-04, four covers, Course B, nut exclusion” on the ledger. The cashier re-types the same facts into the POS. While that re-key remains, three layers fire on the same cover.

1. Payment mismatch. A table-number typo drops the course onto the neighbouring four-top. The host cuts the party to three on the ledger and leaves four on the POS. A 1,000 THB PromptPay deposit is subtracted by hand, or 10% service is applied after 7% VAT instead of before. Voiding in front of the guest becomes the Friday cashier queue.
2. Dead table time. The check closes and the floor does not hear it. Bussing starts late. The loss is real only on Friday night, when the next party is already at the door. A host who looks for an empty chair before calling the waitlist has already missed the resale window.
3. Guest LTV cut. POS membership keys on a phone number. The ledger’s regular keys on a LINE user ID. One person remains two IDs. A guest who spends 80,000 THB a year walks in and the till shows no lifetime. The next course offer and the allergy file never meet the settled check.

Place the arithmetic on a 40-seat Phrom Phong room, 1,100 covers a month, 1,850 THB check average, Friday-Saturday dinner at 18 tables times 2.1 turns.

• Re-key per seating: table number, covers, course SKU, free-text allergy. About 95 seconds. 1,100 covers is about 29 hours. At 90 THB an hour, labour is 2,610 THB a month.
• Billing incidents: four a month, 1,400 THB of discount or re-fire each, 5,600 THB a month, 67,200 THB a year.
• Friday-Saturday seat lag: 7 minutes after payment before the grid turns green. About 30% of those tables have a waiting party. At 1,850 THB and 85 minutes dwell, eight peak nights run about 14,000 THB a month, 168,000 THB a year.
• LTV cut: 35 regulars above 50,000 THB a year treated as first-time walk-ins, with repeat and check down 10%. About 175,000 THB a year.

The 2,610 THB labour line is not a board decision. The body of the loss is unsold second sits and spend that never reaches the card. If you KPI typing time, the meeting returns to “which POS is cheaper per month.” Watch the Friday 20:00 course that landed on the wrong table, and the regular who spent 80,000 THB last year and booked somewhere else this month.

2. Floor notes, Reddit, and X describe the same split

Shop memos and public posts name one structure.

On the floor (ledger and till on separate books). Friday 18:50, LINE confirms “four covers, Course B, 19:00, window.” At 19:05 the host marks Seated on the iPad. The cashier, in a rush, types “4.” The course opens on POS Table 4, which is counter 4. At 19:40 the window table arrives at the till with an empty folio. During the void and transfer, the next party waits at the door.

On X (vendor operations, not menu taste). In May 2026 a FoodStory POS user (Wongnai Media’s iPad line) posted that outage diagnosis was pushed back onto the shop and that support did not move. In May 2025 the same family of products signalled a shift of incident intake from phone to chat. Rooms that used to isolate a frozen till by voice now sit in a chat queue while Friday night dies. Bangkok operator groups repeat a second pattern: Wongnai POS works, and first-time setup assumes Thai copy. A Japanese GM who only read the English UI goes live with table labels and tax classes that do not match the floor.

On Reddit (the structure, product names swapped). r/restaurantowners keeps posting the three-tablet stack: POS, booking site, delivery tablet, same order typed twice. r/KitchenConfidential’s stock story is the floor change that never hits the POS, so the kitchen ticket and the check disagree. Operators are not refusing a brand. They are refusing four gaps: (a) Seated does not open a folio, (b) payment-complete does not return to table state, (c) membership ID is not the same key as reservation ID, (d) during an outage the cloud and the terminal each claim to be the book of record.

The operating implication is simple. Buying Wongnai POS or Ocha is not the same event as killing double-entry on the booking ledger. LINE MAN dropping into the kitchen does not prove that an in-house tasting course will drop onto the till.

3. Feature, price, and constraint matrix

“POS integration” is a slogan. Implementation decides monthly re-key volume and how complete the guest card is. List prices below are public figures from July to August 2026, mostly exclusive of VAT 7%. Daily headline rates move with campaigns.

Read the table as one sentence. Wongnai POS and FoodStory are not rivals. They are Wongnai Media (LINE MAN Wongnai) Android and iPad lines. 14 THB a day is the Android headline. A full-service room that actually quotes will often land on the iPad line near 1,990 THB a month. Ocha at 799 THB is cheap as a till. For a shop that wants guest LTV back on the booking card, “membership cannot connect outside” hits first. StoreHub at 990 THB is an entry for stock and e-commerce. It is rarely why a Bangkok private-room house buys. Rezabo’s 1,900 THB is not POS rent. It is the cost of keeping Wongnai or Ocha in place and joining booking events to payment events on one key.

4. Double-entry dies on three event binds, not on a logo row

Vendor decks stop at “we connect by API.” Design the book of record for each event first.

Event 1. Seated opens the folio. The moment the ledger marks Seated, an empty check appears on the mapped POS table. Course SKU, covers, allergy codes, and deposit balance ride in the payload. The cashier does not re-type the table number. Course changes after seating happen on the POS and write back on settle.

Event 2. Payment-complete releases the table. Cash, PromptPay, card, or split close is received by webhook or by a bounded poll. The ledger moves to “paid / bussing” and offers the table to the waitlist. Spoken “they just got up” is not a book of record. Split tender and partial return release the table only on the final settled amount. A mid-check partial payment must not open the chair.

Event 3. Settled sales attach to the guest card. Tax-inclusive total, line items, discount, tender, service charge, and VAT attach to reservation ID and guest ID. Build the match table for POS member number, LINE user ID, and phone before go-live. Unmatched checks land in an “unnamed sales” queue for the GM the next morning. If unnamed rows are deleted at month-end, LTV does not come back.

A connection that misses any of the three is a dashboard with logos. Next-morning CSV is useful for cover-count versus check-count. It cannot release a Friday table and it cannot inject a course at seating. Do not mix those jobs.

type PosAdapter = "WONGNAI_ANDROID" | "FOODSTORY_IPAD" | "OCHA";

interface SeatedOpenCheckCommand {
  idempotencyKey: string; // reservationId + seatedAt ISO
  reservationId: string;
  posTableId: string;     // internal POS id, never "T-04" display
  covers: number;
  courseSku: string | null;
  allergyCodes: string[]; // codes, not free text
  depositInclusiveSatang: number;
  guestId: string | null;
}

async function openCheckOnSeated(
  adapter: PosAdapter,
  cmd: SeatedOpenCheckCommand
): Promise<{ checkId: string; duplicate: boolean }> {
  const existing = await findCheckByIdempotency(cmd.idempotencyKey);
  if (existing) return { checkId: existing.checkId, duplicate: true };
  return postPartnerOpenCheck(adapter, cmd);
}

The timeout path retries the same idempotencyKey. Two Seated taps, or a LINE retry, must open one folio.

{
  "event": "pos.payment.closed",
  "event_id": "evt_7f3c9a21",
  "occurred_at": "2026-08-14T20:47:11+07:00",
  "shop_id": "shp_thonglo_04",
  "check_id": "chk_88421",
  "pos_table_id": "tbl_12",
  "reservation_id": "rsv_19c0e4",
  "tender": ["promptpay", "card"],
  "amounts_satang": {
    "food_ex_vat": 720000,
    "service_10pct": 72000,
    "vat_7pct": 55440,
    "deposit_applied": 100000,
    "settled_inclusive": 747440
  },
  "line_items": [
    { "sku": "COURSE_B", "qty": 3, "allergy_codes": ["NUT"] }
  ]
}

Receive that payload at-least-once. The same check_id must release a table once.

query GuestSpendOnReservation($reservationId: ID!) {
  reservation(id: $reservationId) {
    id
    guest {
      id
      lineUserId
      phones
      ltvInclusiveSatang
    }
    seatedCheck {
      checkId
      settledInclusiveSatang
      serviceSatang
      vatSatang
      unnamed: matchStatus
    }
  }
}

mutation AttachSettledCheck($input: AttachSettledCheckInput!) {
  attachSettledCheck(input: $input) {
    guestId
    unnamed
  }
}

5. Plan traps and first-year TCO

On sticker monthly, hand-entry on the existing POS looks cheapest, Ocha next, Wongnai Android cheapest still on a daily rate. Add mismatch cost and the cost of re-collecting guest history, and the order changes.

Assumptions (40-seat Phrom Phong, 1,100 covers a month, 1,850 THB check, Friday-Saturday seat lag and billing incidents at the conservative figures in section 1):

• Billing incidents: 67,200 THB a year
• Friday-Saturday missed resale: 168,000 THB a year
• Regulars down 10% LTV: 175,000 THB a year
• Re-key labour: 31,320 THB a year
• Split-stack cost, if all four land: about 440,000 THB a year

They do not all land at full value every year. Billing plus seat lag already clears 230,000 THB. Then add software.

Four traps sit under the stickers. First, 9 THB or 14 THB a day is a headline for a single-site QSR whose main line is LINE MAN. A full-service room that papers that number through finance often discovers it needed the 1,990 THB iPad line. Second, daily deduction nets against settlement, so “POS rent” never appears as a monthly AP line. Third, Ocha at about 8,900 THB a year is cheap as a till, and the work to return members to the booking card is a separate budget. Fourth, a shop-written webhook quote that ignores table maps, splits, tax order, replay, offline queues, and post-transfer credential rotation routinely clears 80,000 to 150,000 THB in year one.

Do not over-claim Rezabo’s number. 1,900 THB a month is the unlimited reservation ledger. Wongnai or Ocha software does not disappear. The value is that booking volume does not turn the ledger into a per-cover meter, and that Seated, payment, and sales-attach are not re-implemented by the shop. Against split cost above 230,000 THB a year, a 19,000 THB ledger line is one order of magnitude smaller.

6. API and infrastructure limits to close before kickoff

Public API presence. TableCheck publishes POS-facing API documentation. Wongnai POS / FoodStory are built around LINE MAN intake and the merchant console. A third-party booking ledger cannot subscribe to the same event grain from a public spec. Connect through a partner contract, an official connector, or a permitted export. If someone says “REST, two-way” in a meeting, take the event list (seated, course inject, split, close, VOID) and the SLA on paper.

Ocha constraint surface. Help pages list no external membership connect, no dynamic QR payment, no QR order, and no delivery connect. Later Scan-to-Order and PromptPay pages disagree. The adapter treats only vendor-guaranteed events as book of record. Do not scrape unpublished screens. Write OAuth client re-issue after operator transfer into the runbook.

Money and tax. Thai full-service arithmetic is commonly ex-VAT course, plus 10% service, plus 7% VAT on the combined base. Decide first whether the reservation deposit is tax-inclusive. Round satang (0.01 THB) the way the POS rounds. If the ledger rounds half-up and the POS truncates, daily reconciliation drifts by a few baht and the floor stops trusting the bind and returns to hand entry.

Identifiers. Do not mix reservation ID, POS check_id, table_id, guest_id, and payment txn_id. Normalise phones: leading 0 versus +66. Moving a folio opened on a secretary’s number onto the principal guest is a logged host action, not a Friday rewrite of the match table.

Transport. Seated payloads carry reservation_id + seated_at as the idempotency key. A timeout retry must not open a second folio. On POS offline (Ocha’s strong case), flush the unsent queue in time order after reconnect. The ledger keeps seating and intake up while the till is dark.

Kitchen printers. Firing ESC/POS course tickets from the ledger onto TCP 9100 doubles print with the POS kitchen route. Print book of record stays on the POS. The ledger hands course SKU to the POS. The POS prints. Allergies travel as codes and print as a red band, not as a novel in the special-instructions field.

Partner adapters that do exist still sit inside unpublished envelopes. Use the following as a planning ceiling, not as a published Wongnai SLA. Confirm every row in the partner statement of work.

CREATE TABLE pos_check_bind (
  reservation_id   TEXT PRIMARY KEY,
  check_id         TEXT NOT NULL UNIQUE,
  pos_table_id     TEXT NOT NULL,
  adapter          TEXT NOT NULL,
  seated_at        TIMESTAMPTZ NOT NULL,
  closed_at        TIMESTAMPTZ,
  settled_satang   BIGINT,
  unnamed          BOOLEAN NOT NULL DEFAULT TRUE,
  idempotency_key  TEXT NOT NULL UNIQUE
);

/* Daily cover vs check recon: unnamed rows are a GM queue, not a delete. */
SELECT
  DATE(seated_at AT TIME ZONE 'Asia/Bangkok') AS biz_date,
  COUNT(*) FILTER (WHERE closed_at IS NOT NULL) AS closed_checks,
  COUNT(*) FILTER (WHERE unnamed) AS unnamed_sales,
  SUM(settled_satang) FILTER (WHERE NOT unnamed) AS attached_satang
FROM pos_check_bind
WHERE seated_at >= DATE '2026-08-01' AND seated_at < DATE '2026-09-01'
GROUP BY 1
ORDER BY 1;

A morning with unnamed_sales above zero is a join job, not a “sync is green” screenshot.

7. Freeze the table map first, then spend three weeks

• Week 1. Copy every floor chair onto the POS internal ID. Tabulate combine tables and private rooms as exceptions. Scope is Friday-Saturday dinner courses only. Walk-ins may stay POS-origin. Match deposit offset and tax order on one test folio.
• Week 2. Run Seated-open and payment-close on live hardware. Exercise split tender, cover drop, VOID, and partial return at least three times each. Fire the payment webhook twice by hand and confirm the table does not double-release. At 16:00 Friday, stop the GM’s verbal check “did you tell the cashier the table number.”
• Week 3. Turn on settled-sales attach. Make the unnamed-sales morning queue a GM duty. Confirm LINE MAN (or existing delivery) tickets do not overwrite in-house reservation IDs. One-page outage rule: pay on POS alone, rejoin on check_id after reconnect.

Widen to all dayparts only after Friday-Saturday course mismatch sits at zero for two weeks. Auto-opening every two-top at lunch on day one explodes table-map exceptions at peak.

8. Questions the GM should close before signing

Q1. Do we have to throw away Wongnai POS or Ocha?

No. Payment, tax invoices, and LINE MAN intake stay on the current POS. What you throw away is re-typing table number and course at every seating.

Q2. Is the Android line enough for a full-service room?

If you run buffet, deep inventory, staff order, or EDC, quote the iPad line (FoodStory). Do not paper an Android daily rate through finance as if it were that quote.

Q3. Will Ocha member points flow back onto the booking card by themselves?

Official help says no external connect. If you need two-way point balances, keep points inside Ocha or design a separate booking-side benefit. Do not decide on a slide titled “CRM integration.”

Q4. If the internet dies, do bookings stop?

They must not. The ledger keeps running. Ocha can still take payment offline. After reconnect, flush unsent events with idempotency. Do not open the same chair twice on paper while the line is down.

Q5. Will joining POS cut reservation volume?

Guests see that they do not repeat the course at the table and that the cashier queue is shorter. Completion rate drops when you spread deposits or membership capture onto every chair, not because the till is joined.

Q6. Do we need an engineer on the floor?

The GM and the floor own the table map and the test folios. Auth keys, webhook signatures, and tax recon live with the implementation side. Resident maintenance that depends on screen scraping breaks on every app update and every operator transfer.

Close: join reservation IDs, not logos

Wongnai POS and Ocha already run Bangkok in-house payment. The missing piece is not another till. It is the bind to booking events. Daily 14 THB headlines, 799 THB offline resilience, a closed membership API, daily settlement deduction, table-number spelling drift: close those in the contract and the map, then automate only Seated, payment, and sales-attach. Double-entry ends after that, not after a logo appears on a status page.

Keep the current Wongnai POS or Ocha. Run seating and payment-complete on one key. Start from the table map and one test folio, not from a generic “we have an API.”