@Andrea ********
seeing as you get an O-A visa from a thai consulate in your country before you wing your way here I'd say look at the website of one of the 4 thai consulates in the USA that can issue a year-long, multi-entry Non-Immigrant Type O-A (Long Stay) visa.
Those are; Chicago, New York, Los Angeles, and Washington DC.
Each consulate has a slightly different set of criteria and how they want the documents presented to them.
You can apply by post at those consulates too.