Hi - I plan to be in Chiang Mai this coming fall, traveling on a U.S. passport. I understand I can get initial 30 day stay without visa / visa exempt I believe is the term. Can I then extend this for another 30 days? If so - what is cost and where can it be done - in Chiang Mai? Finally, what type of documents, tickets, etc are needed 1) on arrival and 2) when applying for extension. I will have a departure airline ticket to exit / return to the U.S. before having been in Thailand for a total of 60 days. My thanks in advance.
TLDR : Answer Summary
Traveling on a U.S. passport, you can initially stay in Thailand for 30 days without a visa under the visa-exempt rule. You can then extend this for an additional 30 days at immigration offices in Chiang Mai, such as at Promenada mall. Required documents for initial entry include a departure airline ticket and potentially proof of sufficient funds (around 10,000 baht for 30 days). When applying for the extension, you may need to provide your local address and incoming flight information.