Service guide
Thai citizenship by naturalisation or marriage: the three routes in the Nationality Act, the 5,000 baht fee, the 730-day standard, and what a firm does.
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Thai citizenship is granted, not accumulated. The Nationality Act B.E. 2508 sets three application routes, and in every one of them the Act states that permission or refusal is the discretion of the Minister. That single fact shapes the whole matter. No firm can promise an outcome, and the work is about building a record that gives the decision its best footing rather than arguing an entitlement.
The three routes are naturalisation under sections 10 and 12, the section 9 route for an alien woman married to a Thai citizen, and a section 12 application by a foreign husband, who is exempt from two of the section 10 qualifications by section 11(4). Most published summaries collapse the second and third into a single genderless marriage route. The Act does not contain one, and applying under the wrong provision is a wasted filing.
Anyone who suspects they may already be Thai by birth, or who is dealing with a decision that has already gone against them, is in the territory of Thai nationality disputes rather than a fresh application.
The three application routes
Requirements as written in the Nationality Act B.E. 2508 (1965), sections 9, 10, 11 and 12, with income and marriage figures from the Department of Provincial Administration's nationality clinic.
| Requirement | Naturalisation (s.10 and s.12) | Foreign wife of a Thai man (s.9) | Foreign husband of a Thai woman (s.12 with s.11(4)) |
|---|---|---|---|
| Who it is for | Any adult foreign national | An alien woman who marries a Thai citizen | A husband of a Thai citizen |
| Residence certificate first | Yes, the five years of domicile are held on a residence certificate or alien identification certificate | Not stated as a requirement; domicile in Thailand with a name in the house registration | The section 10(4) domicile requirement does not apply |
| Five years' domicile | Yes, consecutive, to the date the application is filed | Not stated; three years of registered marriage instead | Exempt under section 11(4) |
| Thai language | Yes, as prescribed by Ministerial Regulation | Not stated for this route | Exempt under section 11(4) |
| Income floor | 80,000 baht a month, or 40,000 with a Thai spouse, Thai children or a Thai degree | The husband's income, not less than 20,000 baht a month | Section 10(3), a well founded occupation, still applies |
| Points assessment | Yes, at least 50 points | Not stated for this route | Applies, as a section 12 application |
| Decision | Minister's discretion, Royal Assent, oath of allegiance | Minister's discretion | Minister's discretion, Royal Assent, oath of allegiance |
| Official application fee | 5,000 baht | Not published in the general-route manuals | 5,000 baht |
Source: Nationality Act B.E. 2508 (1965), sections 9, 10, 11 and 12
Checked August 2026
The most common reason an enquiry is years early is that the five consecutive years of domicile are not a visa question. The Department of Provincial Administration's nationality clinic states the residence requirement and the five-year domicile together: the applicant holds a residence certificate or an alien identification certificate and is recorded in the civil registration. Time spent on renewed long-stay visas does not build that clock.
Permanent residence is therefore the real first step for the general naturalisation route, and it is its own multi-stage application with its own quota. Permanent residency in Thailand covers what that stage takes.
The same clinic page sets the income floors: not less than 80,000 baht a month for a foreign national with no Thai connection, and not less than 40,000 for someone married to a Thai citizen, with Thai children, or holding a degree from a Thai institution. Personal income tax evidence for not less than three years supports the figure, so the income has to have been declared as well as earned. Applicants must also pass a scoring assessment totalling not less than 50 points, speak and understand Thai, and be able to sing the national anthem and the royal anthem. The anthem requirement is written into the department's own service manual, not folklore.
Note: The declaration about your existing nationality
The Nationality Act does not require a naturalisation applicant to prove that the other nationality has ended. Sections 10, 11 and 12 contain no such qualification.
The department's application checklist does nonetheless require a signed declaration of intention to renounce the original nationality, filed with the embassy or consulate of the country the applicant holds it from. That is a statement of intent made at application, not evidence that anything has been given up.
What gives it weight afterwards is section 19(2): continued use of the former nationality is a standing ground on which the Minister may revoke a naturalised person's Thai nationality. The revocation side belongs to the disputes page rather than this one.
Whether the other nationality actually survives is decided by that country's law, not by Thai law, and it has to be checked there.
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What the application costs the state
Fees published in the Department of Provincial Administration's naturalisation service manual.
| Item | Fee |
|---|---|
| Application for naturalisation as a Thai citizen | 5,000 baht |
| Application for a minor child applied for at the same time | 2,500 baht per child |
| Certificate of naturalisation | 500 baht |
| Replacement certificate | 500 baht |
Source: Department of Provincial Administration, naturalisation service manual
Checked August 2026
The amounts above are what the state charges, and they are identical whoever files. Professional fees are separate, set by each firm, and no official or neutral source publishes a market rate for this work, so a page that gives you a figure is guessing.
What is worth knowing is how the engagement usually splits. Assembling and filing the application is bounded work with a definable scope, and many firms will quote it as a fixed fee. The waiting phase that follows is not bounded, because its length depends on the ministries rather than on the firm, so it is normally handled on a retainer or charged stage by stage as the file moves. Ask for both parts in writing, and compare quotes on scope rather than on the headline number: what is included when a department asks for a further document two years in is where the quotes actually differ.
Confirm the route and the residence position
Which section applies, and whether the residence certificate and the five years of domicile are actually in place. This is where an application is either years away or ready.
Assemble the record
Personal income tax evidence for not less than three years, a salary certificate, the non-Thai house registration, bank evidence, and the declaration of intent to renounce filed with your own embassy.
File the application
Bangkok residents file with the Special Branch Bureau. Elsewhere, the filing goes to the Provincial Police.
Interview, language and points assessment
Spoken and heard Thai, the national anthem and the royal anthem, and the scoring assessment with its 50-point minimum.
Ministry of the Interior review and the ministerial decision730 days (published standard)
The department publishes a total processing standard of 730 days for the procedure. It is a service commitment, not a prediction about an individual file.
Royal Assent and the oath of allegiance
Where the Minister decides to grant permission, the matter goes to the King for Royal Assent, after which the applicant takes the oath of allegiance.
Publication in the Government Gazette
Acquisition takes legal effect on publication in the Government Gazette, and the certificate of naturalisation is then issued as proof.
The legal argument in a naturalisation matter is small. The work is evidential, and it is long. Three years of tax records have to agree with three years of salary certificates, the house registration has to match the residence certificate, the marriage record has to be in the form the department accepts, and the embassy declaration has to exist before the file is filed rather than after. Applications fail on inconsistency far more often than on eligibility.
The second half of the job is discipline across a matter measured in years: keeping the record current as documents expire, responding when a department comes back with a request, and knowing which stage the file has reached. A firm that treats this as a filing rather than a matter tends to go quiet after submission.
The section 9 route turns entirely on the marriage record, which has to be a legally registered marriage of not less than three years with the husband's income evidenced from a salary certificate and the previous year's tax filing, as the department's clinic sets out. Where the registration itself is incomplete or was done abroad, marriage registration in Thailand is the piece to settle first.
What no firm can offer is the result. Permission is discretionary in all three routes, and a refusal, along with revocation and loss, is handled on the disputes side rather than here.
The operative moment is not the Minister's decision and not the oath. It is publication in the Government Gazette, which is when acquisition of Thai nationality takes effect, and the certificate of naturalisation is issued afterwards as proof of it. Anyone counting the wait should count to that date.
Thai nationality then carries the documents that follow from it, and the immigration status that governed the years before it stops applying.
Readers who are not yet at the permanent residence stage are still on the long-stay ladder, where the work is visa strategy rather than nationality. Firms and visa agencies in Thailand handle that end of it.
This page is general information, not legal advice. Fees, income floors and procedures change, and permission is in every route a matter for the Minister. For a specific case, speak with a qualified professional.
Sources: Where these figures come from
Routes, qualifications, exemptions, the Gazette effect and the revocation ground: Nationality Act B.E. 2508 (1965), official English translation of the Office of the Council of State as amended to Act No. 5, B.E. 2555, sections 5, 9, 10, 11, 12 and 19.
Fees, the 730-day processing standard, the 50-point minimum, the anthem requirement, the renunciation declaration and the filing points: the Department of Provincial Administration's published service manuals for naturalisation.
Income floors, the three-year marriage minimum and the residence-certificate basis for the five-year domicile: the department's nationality clinic pages for sections 10 and 9. All figures checked on 26 August 2026.
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