An API is the channel that lets two systems exchange data on their own, without a person retyping it. It stands for Application Programming Interface, but the acronym is not the part you need. What matters is whether a given API is self-serve or needs weeks of approval, and what a vendor is really selling when they say "we'll just connect the API." This article answers both, using the APIs a Thai business actually meets.
An API Is the Waiter - but the Menu Matters More
The fastest way to get it is a restaurant:
- •You (Client) = the customer at the table who wants something
- •Waiter (API) = the go-between who takes your order to the kitchen and brings something back
- •Kitchen (Server) = the system holding the data. You don't get to walk in
- •Menu (API documentation) = what you're allowed to order, and you can't order off-menu
That last point is where most projects break. The client wants a field that "surely exists," but the other side never exposed it. Before approving a budget, ask for the link to the doc page proving the data can be pulled.
The APIs a Thai Business Actually Meets
Skip the generic examples. These are the APIs Thai business owners hit in real operations, and how hard each is to get:
| API | What it does | How you get access |
|---|---|---|
| LINE Messaging API | Auto-reply, Rich Menu, broadcast | Open a LINE OA and create a channel yourself |
| Shopee / Lazada Open Platform | Pull orders, push stock levels | Register as developer + shop owner authorizes (OAuth) |
| Bank / PromptPay | Take payments, confirm money arrived | Registered company and a signed agreement |
| Thai address and postcode data | Autofill subdistrict, district, province | Open data, usable immediately |
| e-Tax invoice | Issue electronic tax invoices | Through a certified service provider |
"Self-Serve" vs "Needs Approval" Is Weeks Apart
When scoping, I sort APIs into three tiers, because the tier decides the timeline more than the code does:
- 1.Sign up, key in minutes - LINE Messaging API, Google Maps, Thai address data. Start tomorrow
- 2.Register as a developer, wait for review, shop owner authorizes - Shopee, Lazada, TikTok Shop. Days to weeks, and the person clicking approve must be the account owner, not the developer
- 3.Contract and company documents - banks, payment gateways, tax systems. The longest tier, and hiring a faster developer does not speed it up at all
If tier 3 is anywhere in the project, start the paperwork on day one. Otherwise the system sits finished, waiting weeks for approval.
LINE Messaging API: the Numbers Before You Budget
LINE is the API Thai businesses connect most, and the one budgets get wrong most, because development cost and message cost are two separate bills. LINE OA plan pricing in Thailand (checked against the LINE for Business pricing page on 20 Aug 2026):
| Plan | Per month | Messages included | Overage |
|---|---|---|---|
| Free | 0 THB | 300 messages | Cannot send more |
| Basic | 1,280 THB | 15,000 messages | 0.10 THB / message |
| Pro | 1,780 THB | 35,000 messages | 0.06 THB / message |
Prices exclude 7% VAT, and 300 free messages disappear fast - 300 followers is one broadcast and the month is gone. Check current terms for which message types are counted, since LINE adjusts them periodically. Detail: LINE OA pricing plans
PromptPay and "Auto-Confirm Payments" - the Costliest Misconception
The question I get most: "Is there an API to check whether money landed in my account?" The honest answer is that Thai banks do not let you sign up online and start pulling your own transaction feed. Three routes actually work, each trading something different:
- •Payment gateway - fastest. One signup covers PromptPay QR, cards, and a success notification, in exchange for a per-transaction fee
- •Direct bank API - usually cheaper per transaction at volume, but requires a registered company, a signed agreement, and weeks of onboarding
- •Slip verification - the customer transfers and uploads the slip, your system checks it against a verification service. Good at modest volume because you can start immediately
If you go the slip route, never verify by reading numbers off the image alone. Fake slips are trivially easy to produce. Always check against the source, and block the same slip from being reused on a second order.
Why "Just Connect the API" Is Never Just That
One API call really is a few lines of code. What clients pay for is everything after that - the part where it breaks:
- •Tokens expire - the sync dies at 3am and nobody notices until a customer asks where their order went
- •Data doesn't line up - Thai addresses come in several written forms, phone numbers as both 08x and +668x, marketplace shop names not matching accounting records. Mapping eats more time than the API call, almost every time
- •Rate limits - call too fast and you get blocked. You need a queue and backoff
- •The other side goes down - you must know what was dropped and be able to retry without creating duplicate orders
- •Sandbox is not production - passing tests is not the same as being approved to go live
Most integration work is not calling the API - it is handling the times it doesn't work. If a quote never mentions this, the quote doesn't include the real job.
How Long and How Much
The ranges below are rough scoping brackets by job shape - not a quote, not industry statistics. They exist so you can sanity-check a proposal:
- •One-way, simple logic - web form to Google Sheets to a LINE alert. Days
- •Two-way with state to sync - marketplace orders into stock, then status back out. Weeks
- •Money or tax documents involved - add approval waiting time, independent of how fast your developer works
Do the arithmetic first (illustrative numbers - substitute your own): 60 orders keyed a day at 90 seconds each is 1.5 hours a day, about 33 hours a month. At 100 THB an hour that's roughly 3,300 THB a month. Against a low five-figure baht build, it pays back in a few months. If the saving is 800 THB a month, don't connect anything yet.
Do You Need a Developer, or Will n8n / Make / Zapier Do?
n8n, Make and Zapier ship ready-made connectors for LINE, Google Sheets, email and hundreds more, so business owners really can wire simple APIs themselves. If the job is moving data from A to B at modest volume with simple logic, start no-code - hire a developer when it stops being enough. Write real code when volume makes the platform's monthly bill exceed the build cost, when logic is too complex to drag into blocks, or when customer data means you must control PDPA compliance yourself. Compare in n8n vs Make vs Zapier, example in n8n + LINE OA.
How Webhooks and MCP Differ From APIs
These three get used interchangeably until nobody knows what's being discussed. The clean split is "who starts the conversation":
- •API - you ask, they answer. Right for when you want data now, like pressing a button to pull the latest orders
- •Webhook - they knock on your door when something happens, so you're not polling every minute. Cheaper and much faster. More in What is a webhook
- •MCP - a standard that lets an AI call tools and data itself. The AI-era answer to the same problem. More in What is an MCP server
Real systems use both: a webhook says "new order," then your code calls the API back to fetch that order's detail.
5 Questions to Ask Before Signing an Integration Job
You don't need to code to run this project well. Ask these five and you'll know whether the other side has done it before:
- 1.Is this API self-serve or does it need approval? How many days, and who files the paperwork?
- 2.Is the data I want actually in the API docs? Send me the link to that page.
- 3.If the other side is down for 2 hours, what does the system do, and how will I know what was dropped?
- 4.When do tokens or keys expire, who renews them, and what happens if it expires on a holiday?
- 5.Does this price include support after handover, and what's the charge if the provider changes API version?
If the answer to question 2 is "should be fine" with no link, hold off on signing. That is the number-one cause of integration jobs blowing out.
Arm - CherCode
Full-Stack Developer & Founder
Software developer with 5+ years of experience in Web Development, AI Integration, and Automation. Specializing in Next.js, React, n8n, and LLM Integration. Founder of CherCode, building systems for Thai businesses.
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