As everyone said. No visa needed if you are a us passport holder (and many other countries). Currently it’s 60 days visa exempt (they are talking about lowering it to 30 days, but that would not affect you either). When you arrive, you go straight to immigration, not visa on arrival. That is for countries that are not eligible for visa exempt.
As everyone said above, fill out the TDAC three days or fewer before arriving. You can do it on arrival as well but then you have to wait in line. TDAC is 100% FREE so if it’s asking to charge you anything you’re on the wrong website. Only use the official Thai government one.
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