How is the Thai ID check digit computed?

Multiply the first 12 digits by descending weights 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, sum the products, take the remainder modulo 11, subtract it from 11, and take that result modulo 10. The answer must equal the 13th (last) digit.

How many digits is a Thai national ID?

Exactly 13. It is often printed grouped as 1-2345-67890-12-3, but the tool ignores dashes and spaces, so you can paste either form.

Does a valid check digit mean the ID is real?

No. A valid check digit confirms the number is internally consistent, not that it belongs to a registered citizen. Verifying a real identity requires a Department of Provincial Administration lookup, which this tool does not perform.

What do the leading digits mean?

The first digit indicates the category of the holder (for example 1 and 2 are Thai citizens registered after 1984, 3 those registered earlier), and the next digits encode the province and district registration office. The check digit only validates the whole number's consistency.

Is my ID number sent anywhere?

No. The check is computed entirely in your browser. The ID never leaves your device, so it is safe to paste.

Thailand National ID Validator

The Thai national ID (Personal Identification Number, PID) is the 13-digit number issued to every citizen and printed on the Thai ID card. The final digit is a checksum computed from the first twelve, which lets you catch typos and transpositions instantly. This free validator runs the official Department of Provincial Administration algorithm in your browser.

How it works

The Thai check-digit algorithm uses descending positional weights:

Strip any dashes or spaces, leaving 13 digits.
Take the first 12 digits and multiply each by its weight: 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2.
Sum the 12 products.
Compute remainder = sum mod 11.
The expected check digit is (11 - remainder) mod 10.
The ID is valid if that value equals the 13th (last) digit.

The mod 10 at the end handles the case where 11 - remainder is 10, mapping it back to 0.

Example

For 1101700230705, take the first 12 digits 110170023070 and apply the weights:

(1×13)+(1×12)+(0×11)+(1×10)+(7×9)+(0×8)+(0×7)+(2×6)+(3×5)+(0×4)+(7×3)+(0×2) = 161.

161 mod 11 = 7, so the expected check digit is (11 − 7) mod 10 = 4. If the 13th digit is 5 here, that means this illustrative number would fail — re-check the digits. A valid check digit confirms internal consistency, not registration. Everything runs locally; nothing leaves your browser.