หารบิล 8 คน ไม่ต้องไล่ถาม "โอนแล้วยัง?" — กรอกครั้งเดียว ส่ง QR ใน LINE รู้ทันทีว่าใครจ่ายแล้ว

Source signals

• SIG-20260426-sea-mainland-personal-money-th-promptpay-friend-iou-trust-trail: "No more manual calculations or awkward 'did you transfer yet?' conversations! ... Generate individual PromptPay QR codes for each person, so they can scan and pay you back instantly through their banking app."

What we ship

**Core features (MVP)**

• **No-signup core**: organizer creates split-link without registration (LINE Login optional at claim-payment step). Cookies + URL token = identity. Zero-friction for friends who don't want another account
• Split flow: organizer enters their PromptPay (phone / NID / bank-account), total amount, guests by name. Splits default equal but per-person override
• **Per-person PromptPay QR**: each guest gets unique PromptPay QR with pre-filled amount → scan → bank app opens with amount + receiver pre-filled
• Real-time payment dashboard: organizer opens share-link → sees "5/8 paid" + who paid; marks paid manually from bank statement (or auto-detect via bank-app deeplink callback)
• LINE share: 1-tap "Share split to LINE chat" → each guest gets personal QR in the group thread
• Receipt OCR (PRO 39 THB/mo): snap restaurant receipt → AI extracts items → drag-drop "kim ordered the pad thai (180), Bell the moo kratha (250)"
• Group memory: organizer sees history "Bell always pays first, Gun always last" — soft social-pressure layer without shaming
• Optional currency conversion for travel-trip splits

**Primary user flow**

1. At restaurant — bill 2,400 THB for 8 people. Organizer pulls out phone.

2. Opens splitbill.app (no signup) — pastes total 2,400, types 8 names, gets share-link

3. Sends share-link to LINE group chat: "หารบิลที่ Mo-Kha — กดสแกน QR"

4. Each of 8 taps share-link → sees personal QR (300 THB pre-filled, organizer's PromptPay receiver) → 1-tap "Pay" → bank app opens with amount filled

5. Guest confirms in bank app → organizer sees in bank statement → marks paid in dashboard

6. Pricing trigger: 3 splits/month free, 4th = upgrade prompt 39 THB/mo unlimited + receipt OCR

**What it looks like**

• **Landing**: hero "หารบิล 8 คน ไม่ต้องไล่ถาม 'โอนแล้วยัง?'" + animated GIF: type names → QR generation → LINE share → "5/8 paid" indicator
• **Main app screen** (organizer view): split summary, 8 person tiles with status (paid / not yet), "Send reminder in LINE" button
• **Output / notification**: LINE message template "หารบิลที่ Mo-Kha 2,400 บาท — น้อง Pim, ส่วนของน้องคือ 300 บาท สแกน QR ↓ ขอบคุณค้าาา"

**MVP build plan (5 days)**

• Day 1: backend (Split, Person, Payment), no-signup token-based identity
• Day 2: PromptPay QR generator (TH BoT spec) + per-person QR generation
• Day 3: share-link flow + LINE Share API + bank-app deeplinks (kbank://, scb://)
• Day 4: TH landing + Omise subscription + receipt OCR (Claude) for PRO tier
• Day 5: deploy CF Pages + Railway, soft launch via TikTok #หารบิล + Pantip /food + LINE Open Chat travel groups

Reasoning

PromptPay built ideal payment infrastructure (instant, free P2P, ubiquitous), but the social-coordination layer is broken. Splitwise (dominant global tool) doesn't work natively with PromptPay (requires accounts, no QR generation, USD-first UX). TH-local attempts (Spliteroo, Harntung, Split Bill) are fragmented — no dominant winner — meaning the market is validated but underserved on UX. Our differentiator: **no-signup for guests** (Splitwise's main friction), **per-person PromptPay QR with pre-filled amount** (1-tap pay), **LINE-native share**. Trivial build (5 days): PromptPay spec is open, LINE Share API is public. Distribution is viral — each split = 5-15 potential new organizers. Recurring revenue OK (not extreme): users split 4-10×/month, premium 39 THB/mo for receipt OCR + unlimited splits — typical freemium conversion 3-5%. **Saturated market caveat**: 4 active competitors (Spliteroo, Harntung, Split Bill — Pay Friends, plus Splitwise globally) — must win UX battle, not market battle. Preferred positioning — "Split for friends-who-don't-want-another-app".

Quick competitive read

**CAUTION — saturated market**, 4+ active TH-targeted attempts:

• **Splitwise (global)**: doesn't generate PromptPay QR, requires all to signup, no LINE integration
• **Spliteroo**: TH-targeted, similar concept, but signup required, no LINE-native share
• **Harntung**: TH-targeted, basic split calculator, no QR generation
• **Split Bill - Pay Friends (App Store)**: most direct competitor, generates per-person PromptPay QR. We differentiate via no-signup PWA (vs native-app friction) + LINE Share API native + receipt OCR PRO + cheaper (39 vs 99 THB)
• **i-so-late, Bill-Sharing-TH**: small Pantip utilities, abandoned
• White-space: **no-signup web-PWA + LINE Share native + per-person QR with pre-filled amount + receipt OCR** combined — none. Competitive pressure 4/10 (saturated but no dominant). Win = UX execution.

Initial pricing hypothesis

Freemium: 3 splits/mo free, then 39 THB/mo unlimited + receipt OCR + history. Premium 99 THB/mo — unlimited + multi-currency travel splits + group memory analytics. Low ARPU compensated by viral loop. Better to have 50K active free users (ad inventory + PRO conversion 3% = $25K USD ARR) than 5K paying.

Distribution hypothesis

TikTok #หารบิล / #SplitBill — TH gen Z love sharing friend-money awkwardness. Pantip /food threads soft-launch ("กินบุฟเฟต์ 8 คน หารยังไงดี?"). LINE Open Chat for travel groups (Krabi/Phuket). University Facebook pages (Chula, Thammasat, Mahidol). Reddit r/Thailand expat gatherings. Each split = viral reach (8 friends see app — 1-2 become organizers next time).