Baiwai — Thai Business Document & Contract System

The Problem

Thai freelancers and small businesses still build quotations and invoices in Word or Excel. Totals get retyped by hand, the baht amount in words is written out manually, document numbers skip or repeat, and Thai text often breaks when the file is exported to PDF — vowels and tone marks drift out of place or turn into boxes.

The Solution

Baiwai (ใบไว) turns one form into a print-ready A4 PDF in Thai. You fill in the line items once; the system calculates the totals, writes the amount in Thai words, assigns a document number that never skips or repeats, and produces a file you can send to the customer by email or LINE straight away.

• 6 business document types — quotation, invoice, receipt, billing note, delivery note, and deposit receipt, all from one shared form and one list page
• Convert between documents — turn a quotation into an invoice or receipt without retyping, plus duplicate, status tracking, and original/copy prints
• 85 contract and legal templates — service, employment, construction, agency, copyright/software, and loan/debt-acknowledgement forms, filled in through guided fields
• Issue as a company or as an individual — pick the issuer per document; issued documents lock their issuer details so later profile edits never rewrite history
• Multiple companies per account — each company keeps its own customers, products, and numbering
• Customer and product lists with autocomplete, autosave drafts, search and filters
• Per-type document footers — payment terms and notes saved once per document type and filled in automatically
• Free and Pro plans — 15 free documents a month, or Pro at ฿199/month (yearly saves 17%) through Stripe Checkout and the customer portal
• Public landing, pricing, and an illustrated how-to guide built from real screenshots of the app
• Feedback button on every page plus an admin back office for messages and users

Engineering Highlights

• Thai PDF rendering proven first — a dedicated Phase 0 de-risked font embedding before any feature work; the same HTML/CSS template drives both the live preview and the generated PDF (headless Chromium)
• Money as integer satang — no floating-point totals; VAT, withholding tax, and discounts round by one shared rule
• Gap-free document numbers (QT-2026-0001 style) assigned only on save, tested against a real database
• Thai-aware sorting — PostgreSQL with the ICU th-TH collation so Thai names sort correctly
• Automated smoke tests — end-to-end Playwright suites for documents, conversion, contracts, multi-company, billing, and feedback

Result

Live at baiwai.nattang.me: a Thai-first document system where a quotation goes from blank form to a clean, correctly numbered PDF in a couple of minutes — with contracts, multi-company support, and paid plans on the same foundation.