- Currently If a U.S. citizen is receiving Social Security payments directly into a U.S. bank account and does not bring the funds into Thailand until the following tax year, they are not subject to Thai tax. Also you only pay tax above a certain level - e.g. the UK pension is unlikely to reach a significant tax level.
If you have foreign-sourced income, you must obtain a tax ID number and file an annual tax return. These changes will come into effect on 1st January 2025 - If you live in Thailand for over 180 days in a calendar year, regardless of your visa status, you’re considered a Thai tax resident.
there is a move to introduce taxes on expats living in Thailand over 180 days - this will be on ANY income coming into the country regardless of whether or not it has been taxed at source.