Thank you for the details.
So, you could somehow register your marriage in Taiwan without registering it in Thailand because you married at a their plase. Then you could apply for your resident visa in Ho Chi Minh City instead of Thailand. It may be because your marriage was already registered in Taiwan? Proof of your marriage registered in Thailand issued by authority of Thailand and authenticated by TECO was supposed to be submitted, but TECO in Ho Chi Minh City accidentally accepted some different documents because they are not familiar with Thai documents, right?
So, there is not any situation that Thai people don’t need to register a marriage in Thailand to get an ARC, but it is more like your ARC was issued by some mistake at TECO.
Thank you again for the details. Things became clear and I feel relieved now.
