You're a little behind the times there
@Mark *******
๐ฎ
First there is no such thing as a "tourist visa on arrival" ๐
If you hold a US passport and show up here without having bought a visa from a thai consulate beforehand you get in free on what's called a "visa exempt" entry. It's not a tourist visa, it's not a visa on arrival, it's not any visa at all, just a free entry stamp
AND
Since July 15, 2024 the free 30 day entry stamp went to 60 days for 90+ countries (including the US)
So when you show up in January you will be stamped in for 60 days ๐
You can indeed get one 30 day extension on the free 60 day visa exempt entry stamp at the immigration office after you're here for 1900 baht.