How does the check-digit validation work?

The Thai National ID uses a mod-11 check digit. The tool multiplies the first 12 digits by weights 13 down to 2, sums them, then computes (11 - (sum mod 11)) mod 10. The card is valid only if that result equals the 13th digit.

How accurate is the validator?

The check-digit test is exact and uses the official algorithm, so it catches typos and many invalid numbers. A number that passes is structurally consistent but the tool never confirms it belongs to a real, registered person.

Is my National ID sent anywhere?

No. This tool is privacy-first — all processing happens locally in your browser and the number never leaves your device.

How many digits is a Thai National ID?

Exactly 13 digits, often written in the grouped form 1-2345-67890-12-3. Dashes are optional here and stripped automatically.

What does the first digit mean?

The first digit is the person type. For example, 1 and 2 are Thai citizens registered after 1 January 1984, 3 is a citizen present in the 1984 household registration, and 8 is a foreigner with permanent residence or a naturalised Thai.

What do the next digits encode?

Digits 2–3 are the province code of registration and digits 4–5 are the district (amphoe) code, followed by registration and sequential numbers, ending in the check digit.

Does a valid check digit mean the ID is real?

No. It only means the number is internally consistent and free of common typos. Confirming a person exists requires the official government registry, which this offline tool never contacts.

Thailand National ID Validator

Thailand National ID validator

This tool validates a 13-digit Thai National ID (เลขประจำตัวประชาชน) using the official mod-11 check-digit algorithm, and decodes the structural fields embedded in the number. It is for HR and KYC checks, form validation, and anyone confirming a typed ID is internally consistent.

How it works

The ID is 13 digits. The first 12 carry the data and the 13th is a mod-11 check digit. The tool computes it by multiplying digit i (1-indexed) by weight (14 − i) — that is weights 13, 12, … down to 2 — summing the products, then:

check = (11 − (sum mod 11)) mod 10

The number is valid only when this matches the 13th digit. It also reads the structural fields:

Digits	Meaning
1	Person type (citizen category / residency)
2–3	Province code of registration
4–5	District (amphoe) code
6–12	Registration and sequential numbers
13	Check digit

Example

For 1101700230708, the weighted sum of the first 12 digits is 146; 146 mod 11 = 3, so check = (11 − 3) mod 10 = 8, which matches the 13th digit — the ID passes. The tool runs this exact calculation on whatever you enter and reports a match or mismatch, along with the person type (here digit 1 = Thai citizen registered after 1984) and the province/district codes.

It is privacy-first: the validator checks the number’s internal consistency only and never queries any government database — nothing leaves your browser.