I am currently a US passport holder in Thailand I arrived on a 90 day type O. Visa, I am wondering, can I extend that while I am in Thailand or do I have to leave and come back in to get 60 more days? It is single entry visa.
TLDR : Answer Summary
A US passport holder in Thailand with a 90-day Type O visa cannot extend the visa while in the country, except in specific circumstances (such as being married to a Thai or having a Thai child). The only option is to leave Thailand and re-enter for a new 60-day visa exemption, or apply for a one-year extension under specific conditions.