Did not have a problem getting a Visa. You need to show that your girlfriend has a reason to return to z Thailand. Mine had a secure job, a good bank account, car and home ownership. They don't mind you coming to visit, they just don't want you to stay there
his wife will need a re-entry permit if she is planning to be out of the US longer than a year, otherwise they will consider she has abandoned her permanent residency and lose her green card
Got my then fiancee a US Tourist Visa. It wasn't difficult except for the paperwork. The main thing is you need to show is that you have a reason to return to Thailand. Property ownership, good job. They just don't want you to come and then stay...