Updated 03-Aug-2025
This information is specifically about Thailand and the United States, though it may later be expanded to other countries, their rules, and traditions.
United States
- Allows dual nationality.
Thailand
Two passports (from the United States)
- Sometimes this is called concurrent passports, though usually second passports.
- Under certain conditions it is possible to apply for and have a second US passport (both being active), though the will not have the same passport number.
- The second passport will be marked as a second passport, and can be renewed thereafter.
- It is unclear how actually difficult this is, or what documentation makes it easier to be accepted by US Immigration (affidavits by passport holder and / or documents by employers stating the case).
- It seems to me that the very nature of passport renewal is risky (using postal service abroad and a 6-8 week time frame on return), especially if one is residing in a country which requires a passport (with valid visa) be carried at all times (such as Thailand).
Two passports (from Thailand and the United States)
- It is legal to have both a Thai and a US passport.
- When entering and leaving the United States, use the US passport.
- When entering and leaving Thailand, use the Thai passport. (Note, if using the US or other non-Thai passport, but being a Thai citizen.)
- When entering and leaving a third country, use whichever passport is best for the situation, e.g., visa-free travel in ASEAN is a part of a Thai passport.