You don't even bother to say what country you are from or visa type..however if coming on 60 day visa exempt you already seem to know it will be a problem... just book a camcelable round trip so you can modify your return once you get an extension... otherwise you probably in for a very miserable vacation after being denied and sent back home immediately.
Being on probation he's not allowed to travel anywhere,.especially out of the country. Probably wouldn't have any issues getting to Thailand but he would be in major trouble if he ever comes back.