Do you need a special visa to go from the usa?? If so, how do you get it?
As FF mentions, the default US visa is 30 days (meaning, you don't have to apply, and this is stamped in your passport on arrival). If you want to stay a little bit longer and avoid the hassle of a visa run, you can get a 60 day tourist visa from the Thai embassy/consulate.
http://www.thaiembdc.org/consular/visa/Tourist.aspx
(Note that the Thai embassy webpage misbehaves under some non-IE browsers)
I've been told, but have not personally confirmed, that these 60 day visas can be extended for an additional 30 days while in Thailand.