Thai National ID Validator
Free Thai national ID validator. Runs in your browser - no data leaves your device.
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What is Thai National ID Validator?
A Thai National ID Validator checks whether a 13-digit citizen ID number is structurally valid. Every Thai ID card number ends with a check digit computed from the first 12 digits, so most typos and made-up numbers fail instantly. This tool recomputes the checksum in your browser and also decodes what each block of digits means: person category, birth year and sex, registration province, and serial number. Nothing is uploaded - the validation logic runs entirely on your device.
Key Benefits
- Catches typos instantly before they reach a database or form submission
- Decodes digit meaning: category, birth year, sex, province, serial, check digit
- No server round-trip - results appear as you type, works offline after loading
- Clear failure reasons: non-numeric, wrong length, or checksum mismatch
- Zero privacy risk - the ID number never leaves your browser
Common Use Cases
- •QA teams testing Thai ID input fields with valid and invalid checksums
- •Data entry staff verifying hand-written or scanned ID numbers before saving
- •Developers generating test fixtures for forms that require citizen ID validation
- •Back-office teams cleaning legacy data with suspected digit errors
How to Use the Thai National ID Validator
- Paste or type the ID: Enter the 13-digit number from the front of the citizen ID card. Spaces and hyphens (e.g. 1-2345-67890-12-3) are stripped automatically.
- Watch the live verdict: The tool validates as you type: green means the MOD-11 checksum passes, red means the number is invalid with the exact reason shown.
- Read the digit breakdown: Each digit block is explained: digit 1 is the person category, digits 2-5 encode birth year/sex/province, digits 6-12 are the serial, and digit 13 is the check digit.
- Check the province hint: For IDs issued after 1984 the digits 2-5 map to a registration province - the tool names it with a note that it reflects registration, not necessarily birthplace.
Key Features
- Validates the official MOD-11 checksum used on Thai citizen ID cards
- Explains each digit block: person category, birth year + sex, province, serial, check digit
- Instant live validation as you type - no button click needed
- Tolerates spaces and hyphens so pasted IDs with formatting still validate
- Shows the expected check digit next to yours when a number fails
- Runs 100% client-side - ID numbers never leave your browser
Frequently Asked Questions
What does the last digit of a Thai citizen ID mean?
Digit 13 is a check digit computed from the first 12 digits using a MOD-11 style algorithm: each digit is multiplied by a weight from 13 down to 2, the sum is taken mod 11, and the result is subtracted from 11 (mod 10). This tool recomputes it and compares against the number you entered, so a single mistyped digit is caught immediately.
Can this tool confirm that an ID number belongs to a real person?
No. A valid checksum only proves the number is arithmetically well-formed, not that it is registered to a living person. Confirming a real registration requires the official database, which only authorized government systems can query. Use this tool for format and checksum checks, such as catching typos in data entry.
Does digit 1 tell the birth month or sex of the person?
No, digit 1 categorizes the person: 1 = person born in 1983 or earlier, 2 = person born in 1984 or later, 3 = person born or domiciled abroad, 4 = Thai monk/missionary living in Thailand, 5 = foreigner with residence in Thailand. Sex is encoded in digit 2 together with the birth year (roughly last two digits of the year): odd for male, even for female.
Why does the province shown not match where the person was born?
For people born from 1984 onward, digits 2-5 encode the civil registration office province at first registration, usually the birthplace or family home at that time. People can and do move their registration later, and birth abroad maps to codes 00-4X, so treat the province as a strong hint rather than a guarantee of birthplace.