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Under the US–Thailand tax treaty, US Social Security paid to a Thai resident is taxable only in the United States, so Thailand does not tax it. Money from a 401(k) or IRA works differently: it doesn't get the same automatic exemption, and once you're a Thai tax resident, bringing that money into Thailand can create taxable income here under the remittance rule — though exactly which treaty article applies, and to which part of the payment, isn't settled for every plan. If you are a US citizen, the US still taxes this income under its own rules, wherever you live.
In short
- Social Security is taxed only in the US (Article 20(2) of the treaty).
- A 401(k) or similar employer-plan distribution is generally treated as a private pension; whether that also covers IRA distributions and lump sums isn't officially settled. For a Thai tax resident, bringing the money in can create taxable income here.
- A US government-service pension is taxed only in the US, unless you are a Thai national.
- US citizens remain subject to US tax rules on this income wherever they live, under the treaty's saving clause.
- You become a Thai tax resident once you spend 180 days or more in Thailand in a calendar year.
Which article covers which payment
The treaty sorts US retirement income by article, and the article decides which country taxes it.
| Income | Treaty article | Taxed where |
|---|---|---|
| Social Security | Art. 20(2) | Only the US |
| 401(k) and other employer-plan pensions | Art. 20(1), as advisers apply it | Thailand, once you're a resident and remit the money |
| IRA distributions and lump sums | Not officially settled | Check your specific payment before relying on a rule |
| Private annuity meeting Art. 20(3)'s definition | Art. 20(3) | Thailand, once you're a resident and remit the money; US citizens still answer to US tax rules |
| US government-service pension | Art. 21(2) | Only the US, unless you're a Thai national |
| Roth IRA | — | No official guidance yet |
Social Security under the US–Thailand treaty
The US–Thailand income tax treaty has been in force since 15 December 1997. Article 20(2) gives the United States the exclusive right to tax Social Security paid to a resident of Thailand, and Thailand does not tax it.
This is one of the few payments that escapes the treaty's saving clause — the rule that otherwise lets the US keep taxing its own citizens on everything, everywhere. Article 1(3)(a) carves out specific exceptions to that clause, and Article 20(2) is one of them, alongside Article 20(5) and a handful of others. In practice that means Social Security stays out of Thai tax even for a US citizen living in Thailand.
401(k), IRA and private pensions: a different article
Article 20(1) and Article 20(3) cover private pensions and annuities — pensions paid for past employment, and annuities meeting the treaty's definition: a stated sum, paid periodically at stated times over a stated number of years, under an obligation to make the payments in return for full and adequate consideration other than services rendered. These are taxable only in your country of residence. For a Thai tax resident, that means Thailand, and only once you remit the money.
The treaty text does not mention 401(k) or IRA accounts by name. Thai tax advisers treat 401(k) and similar employer-plan distributions as pensions under Article 20(1); whether that extends to IRA distributions and lump-sum payments in the same way is not officially confirmed.
Under Revenue Department Instructions Por. 161/2566 and Por. 162/2566, foreign income earned from 1 January 2024 while you were a Thai tax resident is taxable when you bring it in, whatever year the transfer happens — income earned in a year you were not a Thai tax resident falls outside this rule. So if a 401(k) withdrawal is treated as income arising in a year you're a Thai resident, moving it to a Thai bank account while you remain a resident can fall inside that rule — but exactly when a distribution "arises" for this purpose, and whether your own contributions can be carved out, isn't settled.
What the treaty does not settle — and no official Thai or US guidance has closed this — is whether Article 20(1) extends to a lump-sum withdrawal the same way it covers a periodic pension payment, and what happens to a Roth IRA, where the money was already taxed in the US before it went in. We don't guess at either answer; we treat them as open until the Revenue Department says otherwise.
On the US side, the IRS still applies its own rules whatever Thailand does. A withdrawal before age 59½ usually carries an additional 10% tax on the taxable part of the distribution, unless one of the IRS exceptions applies — for a 401(k), one exception covers withdrawals from age 55 if you separated from that employer at or after reaching that age. Required minimum distributions from a traditional IRA must start by 1 April of the year after you turn 73; the original owner of a Roth IRA has no RMD requirement. And a US citizen cannot opt out of US withholding on a retirement payment sent abroad, even to a Thai bank account.
US government pensions
Article 21(2) gives the United States the exclusive right to tax a pension paid for government service, as long as the recipient is not a Thai national. We don't name specific US schemes here, because the treaty speaks only to government-service pensions in general, and how it treats every US retirement programme individually is not something the Revenue Department has confirmed in public guidance.
Showing the exemption on a Thai return
If your only US income is Social Security, the Revenue Department has not published guidance on how — or whether — to show that exempt income on a PND 90 or PND 91 return, or which documents it expects to see. Our lawyers look at this with each client individually: we typically suggest keeping the payer's statement showing the source of the funds, in case the Revenue Department asks a question later.
For 401(k) or IRA money that you do remit, the part that counts as assessable income under the rules above is reported on the annual return for the year you bring it in, like other remitted foreign income — but working out which part that is, and when the underlying income arose, needs checking for your specific plan and distribution before you file. If that's your situation, our Thai tax return support covers getting your Tax ID and filing the return itself.
Remittances and the 180 days: what to plan
Thai tax residency turns on the 180-day residency rule: spend 180 days or more in Thailand in a calendar year, and you're a resident for that year. Below that, Thailand taxes only Thai-source income, and a 401(k) or IRA withdrawal you bring in stays outside Thai tax.
One practical problem has no official answer yet: if Social Security and a 401(k) distribution land in the same US account and you then wire a single sum to Thailand, there's no published rule on how to split that transfer between the exempt part and the taxable part. Until the Revenue Department addresses mixed remittances, we recommend keeping Social Security and retirement-account withdrawals in separate accounts, or at minimum keeping a clear paper trail of which transfer came from which source. Our guide to remitted foreign income covers how the remittance rule works more broadly, and a related typical case, savings remitted after 180 days, shows how that distinction can play out in a hypothetical scenario.
A second question comes up with American retirees holding dual tax residency — a typical case, a US citizen on a DTV with two tax residencies, illustrates how Social Security, a private pension and Thai-source income can each need separate treatment.
What to do next
If you receive Social Security, a 401(k), an IRA or a US government pension and you're spending more than half the year in Thailand, the practical questions are usually: which article applies to each payment, when you'll cross 180 days, and how a transfer this year affects your Thai filing. Our team can walk through your specific sources of income on a 45-minute consultation [прайс] and tell you what, if anything, needs to go on a Thai return. We also help with general tax guidance for foreigners in Thailand if your situation involves more than US pensions. Write to us and we'll reply within 24 hours with a plan and the cost, agreed before we start any work.
