Thanks in advance for your help
Asking for a friend who is a Thai national (female) married to an American citizen and living in the USA but does not have a registered Thai marriage. She still has her Thai I.D in her maiden name.
If they wanted to move here permanently, can he apply for a non imm O visa based on marriage at a Thai consulate in America or do they have to visit Thailand and get a registered marriage here first.
TLDR : Answer Summary
A Thai national married to an American citizen can indeed apply for a Non-Immigrant O visa based on their marriage registration in the U.S. They do not need to register their marriage in Thailand before applying for the visa at a Thai consulate in America. However, once they move to Thailand, it is advisable to register their marriage in Thailand as well, which will facilitate the visa extension process and comply with immigration requirements.