How does the Thai ID checksum algorithm work?

Multiply each of the first 12 digits by the weights 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2 respectively. Sum all products. Compute remainder = sum % 11. The check digit (13th digit) must equal (11 − remainder) % 10.

Is my ID number safe to enter here?

Yes. All validation is performed entirely in your browser using JavaScript. No data is transmitted to any server. The input never leaves your device.

Can a number pass the checksum but still be invalid?

Yes. The checksum only verifies the mathematical structure of the number. An ID that has never been issued, has been cancelled, or belongs to a deceased person would still pass the checksum check.

What does the first digit of a Thai ID number represent?

The first digit indicates the registration type: 1 = person with a house registration at birth, 2 = person registered late, 3–4 = Thai nationals registered abroad or after census, 5 = person who immigrated and received citizenship, 6 = non-Thai with permanent residency, 7 = child of non-citizen, 8 = foreigner with a temporary status.

Thai ID Validator

Validate Thai national ID card numbers using the official checksum algorithm.

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Thai ID Number (13 digits)

Enter 13 digits (0/13 entered)

›How validation works (algorithm)

Thai ID Checksum Formula:

Multiply digits 1–12 by weights 13, 12, 11, …, 2
Sum all products
Compute remainder: sum % 11
Check digit = (11 − remainder) % 10
Must equal the 13th digit

How to Use

1
Type or paste your 13-digit Thai national ID number into the input field.
2
The number is auto-formatted as X-XXXX-XXXXX-XX-X as you type.
3
After entering all 13 digits, the result (Valid ✅ or Invalid ❌) appears immediately.
4
If valid, use the Copy button to copy the formatted ID number to your clipboard.

Use Cases

Form validation before submission

Quickly verify a Thai ID number is structurally valid before submitting it in an online form or government portal.

Developer testing

Developers building apps that require Thai ID input can test the checksum logic and validate sample numbers during development.

HR onboarding verification

HR staff can quickly check that an ID number entered by a new employee has the correct format and checksum before storing it.

Typo detection

Detect common transcription errors — a single wrong digit will cause a checksum mismatch, flagging the problem instantly.

Frequently Asked Questions

Thai ID Validator instantly checks whether a 13-digit Thai national ID number is valid using the official government checksum algorithm. No data is sent to any server — all validation happens locally in your browser.

No. The tool only checks the mathematical checksum to verify the number is structurally valid. It cannot confirm identity or whether the number is assigned to a real person — that requires access to official government databases.

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