Upon further reflection and investigation I would strongly recommend that the OP get a 60 day tourist visa in the U.S.A. prior to departing for Thailand. In addition to the issues raised already, many of which are relatively minor, and could probably be addressed by a 500 THB fine at most, I would point out that some carriers occasionally deny boarding to passengers going to Thailand who appear to have an itinerary that includes an over-stay. This usually happens only with PAX on a one-way ticket, but having a valid visa (60-day tourist) in the OP's case would remove this as a potential issue. Again, the odds of having any significant problems are one in a million, but obtaining the 60 day tourist visa seems like an easyway to safeguard against any undue stress?