Dual citizen: which passport do I use for Thailand?

Two passports in one bag and a family waiting on the other side of immigration. It’s a very normal moment to stand in the queue wondering which passport to hand over. Here’s what official pages actually say, and where they go quiet.

What do official pages say, in short?

Leave Thailand on the same passport you used to enter. That’s the one rule we found in writing from Thai embassies. Canada says you must; the UK says it is best.

• Enter on your Thai passport: you arrive as a Thai national. We found no official page that sets a stay limit for that.
• Enter on your other passport: foreigner rules apply. Since 15 September 2026, the visa-free stay for tourism is up to 30 days if your country is on Thailand’s visa-exemption list.
• Getting home: your other country decides which passport you show there.

We found no official Thai page that says you must pick one passport over the other to enter. Embassies explain what happens with each choice.

Do I have to leave on the same passport I entered with?

Yes, according to the Thai embassies that write about it. The Washington DC embassy has a consular note, first written in 2016 and reposted in January 2024, that cites the Department of Consular Affairs at Thailand’s Ministry of Foreign Affairs. In our translation from Thai, its first point says: the passport a traveller uses to enter the country is the one they must use to leave.

The note explains why. If you mix passports, the immigration database ends up with half a trip on each one:

• A foreign passport used to enter but not to leave never gets an exit record, so it can look like an overstay.
• A Thai passport used to leave has no entry record to match.
• Paris adds that entering on a Thai passport and leaving on a foreign one can lead to an overstay charge.

The Paris embassy’s page says the same and adds, in our translation, that immigration officers do not allow travellers to pass through immigration on the way in and out on different passports. It warns that this can lead to an offence of entering or leaving illegally.

Other governments agree:

• Canada: “If you are a dual citizen, you must enter and exit Thailand with the same nationality passport.”
• UK: “If you’re a dual national, it is best to leave Thailand on the same passport you used to enter – this will avoid problems at immigration.”

What happens if I enter on my Thai passport?

You arrive as a Thai national. Thailand’s 2017 Constitution says, in an English translation: “No person of Thai nationality shall be deported or prohibited from entering the Kingdom.”

The embassy notes describe stay limits, visas and extensions only for people who enter on a foreign passport. We found no official page that sets a time limit for a Thai national on a Thai passport. Then you leave on the same Thai passport.

The digital arrival card. The Thai embassy in Mexico says that since 1 May 2025, “all non-Thai nationals entering Thailand by air, land, or sea” must complete the Thailand Digital Arrival Card online within 3 days before arrival. GOV.UK says the same for “all foreign nationals”. Canada’s advice says “All travellers must complete a digital arrival card” and doesn’t mention Thai nationals. None of these pages says what a dual national arriving on a Thai passport should do. If you’re unsure, ask your embassy. If you fill in the card, use only the official government site.

What happens if I enter on my other passport?

You’re treated under the rules for that nationality. Both Thai embassy notes say a traveller on a foreign passport gets the stay their visa or visa exemption allows, must leave before it ends, and has to apply for any extension at the immigration office as a foreigner.

From 15 September 2026, the Danish embassy in Bangkok says visitors “will be given 30 days” when they enter under the visa exemption scheme. Trade press reports that the list covers 60 countries and territories. For British citizens, GOV.UK says visa-exempt entry means “you can stay for up to 30 days for tourism only”, not business, and that visa-exempt tourist entry over land borders is “normally limited to 2 entries per calendar year”. Check whether your other country is on the list. Thirty days matters for long summers with yai, or a few months of living in Thailand.

(The Paris and Washington DC pages give example visa lengths, such as 60 days for a tourist visa. These are examples, not the visa-free stay. Check the current terms of any visa you hold.)

GOV.UK also says the overstay fine is 500 baht a day, up to 20,000 baht, and that overstayers risk detention, deportation and a ban on returning for up to 10 years. That’s written for foreign visitors. We found no official page on how it applies to a Thai national who entered on a foreign passport. See “What we couldn’t confirm” below.

Which passport do I show to get back into my other country?

That’s your other country’s rule, not Thailand’s.

• United States: “U.S. nationals, including U.S. dual nationals, must use a U.S. passport to enter and leave the United States.”
• United Kingdom: “When returning to the UK, British citizens must carry a valid British passport or certificate of entitlement.”
• Sweden: the Swedish embassy in Bangkok says both Sweden and Thailand accept dual citizenship. We found no Swedish page on which passport to show when entering or leaving Thailand.

So one way the rules fit together for a US citizen: leave the US on the US passport, enter Thailand on the Thai passport, leave Thailand on the Thai passport, and enter the US on the US passport. Every border sees one passport for its own in-and-out. Check how this works for your own countries before you book.

Does it matter for help from my other country?

It can. GOV.UK says that as a dual national, “you cannot get diplomatic help from the British government when you are in the other country where you hold citizenship.” Canada says that if Thai authorities consider you a Thai citizen, they may refuse to give you access to Canadian consular services. It’s worth knowing before a long stay, not a reason to panic before a short visit.

Canada’s travel advice says dual citizenship is not legally recognized in Thailand, so official pages differ; see our dual citizenship guide.

What about airline check-in?

Airline check-in and immigration are different checks. We found no official Thai page on what airlines ask dual nationals for. If you’re entering Thailand on your Thai passport and your ticket is booked on your other one, ask your airline before you fly.

Don’t have a Thai passport yet?

If a parent is Thai, you may be eligible for Thai nationality. Our guide Should I get my Thai passport? walks through the documents, from Thai birth registration to the passport (หนังสือเดินทาง, nang-sue doen-thaang). For a child, the first step is to register the birth at a Thai embassy. Whether your other country lets you keep both is covered in Thai dual citizenship for Sweden, the UK and the US.

Thai men with two passports may also have military registration to think about. That’s a separate question from which passport you show at the border, covered in Thai military service for luk khrueng men. The Thai paperwork words are in the glossary.

What we couldn’t confirm

We only publish what an official page says. These questions have no official answer we could find:

• a current Immigration Bureau page on which passport a dual national should use. The embassy notes we rely on are from 2016 (Washington DC, reposted in 2024) and undated (Paris)
• whether a Thai national on a Thai passport has any stay limit
• whether a Thai national on a Thai passport should fill in the digital arrival card
• what happens to a Thai national who entered on a foreign passport and stayed past the visa-free period
• what airlines require from dual nationals at check-in

Thailand’s Ministry of Foreign Affairs passport FAQ says a Thai national who holds a foreign passport may apply for a Thai e-passport, but it doesn’t say which one to use at the border. We re-check this guide at least every 90 days.

Thai words on this page are a draft until a native speaker has reviewed them.