So, My wife and I are thinking about moving to Thailand. She is Thai and has her green card. I understand that she will loose her green card after staying 6 months out of the country. So my question is, does anyone know how difficult it is and how long it takes to get a visa for her to come visit the US for a couple of weeks?

Shouldn't be too difficult if you do your home work, research all the threads in Thaivisa regarding the requirements and make sure you clearly document your long marriage, your long stay credentials in Thailand and her "compelling reason to return" to Thailand.

If she got her green card based on her relationship with you and you remain in Thailand while she visits the U.S. for a legitimate reason, well stated, should be ok as her compelling reason to return would be your long marriage and existing relationship. If she is over 30 and has a good life with you in Thailand, why would she want to overstay in the U.S. and support herself by working in a Thai restaurant.

If you, however, remain in the U.S., her ties would be with you and the overstay potential would skyrocket.