Bank of Thailand Exchange Rate API: Official THB Rates as JSON

The Bank of Thailand publishes the official exchange rates that accounting, tax, and customs practice in Thailand reference — published official rates, not moving market prices. This guide shows how to pull them as JSON: via a REST endpoint or the zero-dependency bank-of-thailand-exchange-rate npm package.

Three kinds of number in one daily table

BOT’s daily release carries the weighted-average interbank USD/THB rate — the canonical Thai reference, served as rate_type: "reference" — plus average commercial-bank counter rates for 19 major currencies and market crossing rates for 29 more, each as separate buy and sell rows. Quoting units (per-100 yen, per-1,000 rupiah) are already normalised to per-1-unit values.

Why official rates, not market rates

A live mid-market feed answers "what is USD/THB trading at right now?" — the right tool for checkouts and dashboards. But accountants, auditors, and tax authorities ask a different question: "which rate were you required to use for this date?" That answer comes from the Bank of Thailand’s published rates, and it never changes after publication.

Get the latest rates (REST)

curl "https://allratestoday.com/api/v1/central-bank/bot/latest" \
  -H "Authorization: Bearer YOUR_API_KEY"

The response is the bank's most recent published table — every rate and the publication date. The latest rates are available on every plan, including the free tier (300 requests/month, no credit card).

The npm SDK

npm install bank-of-thailand-exchange-rate

import { getRate, getLatestRates } from 'bank-of-thailand-exchange-rate';

// One pair at the official rate
const pair = await getRate('USD', 'THB', { apiKey: 'art_live_...' });
console.log(pair.rate, pair.rate_date);

// The bank's full published table
const table = await getLatestRates({ apiKey: 'art_live_...' });
console.log(table.rate_date, table.rates.length);

Zero dependencies, TypeScript types included, and it runs anywhere fetch exists — Node 18+, Bun, Deno, and edge runtimes.

Historical rates for an invoice date

import { getRatesForDate, getHistory } from 'bank-of-thailand-exchange-rate';

const day = await getRatesForDate('2026-08-18', { apiKey: 'art_live_...' });

const series = await getHistory(
  { source: 'USD', target: 'THB', from: '2026-01-01' },
  { apiKey: 'art_live_...' }
);

Historical dates and time series need a paid plan; the latest rates stay free.

Published vs derived pairs

If the Bank of Thailand does not print a pair directly, the API resolves it from the bank's published rates — an inverse, or a cross via THB — and flags it derived: true with the method used. Official and computed values are never silently mixed, which is exactly the distinction an auditor will ask about.

The archive

The daily table is published every Thai business day around 18:00 Bangkok time, and the archive of the interbank rate and the 19 majors reaches back to January 2002.

FAQ

Does the Bank of Thailand have an official exchange rate API?

The bank publishes its official rates on its own site, and AllRatesToday serves the same published rates as clean JSON via REST or the bank-of-thailand-exchange-rate npm package. The latest table is free.

How do I get the official Thailand exchange rate for a past date?

The rates-for-date endpoint returns the official table for any archived date; non-publication days resolve to the most recent published date and are flagged, so audit trails stay honest. Historical dates require a paid plan; latest rates are free.

Which Bank of Thailand rate should an invoice or filing cite?

The weighted-average interbank rate is the standard USD/THB reference in Thai practice; the buy/sell rows are the average commercial-bank counter rates BOT publishes alongside it. All carry the bank’s own publication date.