If the US is anything like the Brits you will need a bulletproof reason for her having to return to Thailand. They don't mind her coming they just don't want her to vanish and stay. Probably 20k baht ($600) is the going rate nowadays but I would be asking about his success rate. Good luck.
Long term rental depends on 'how long'. The rule of thumb or guesstimate here is monthly rent is
*****
th of the property value. So if you are here for the long haul then buy. I know two people who have been here almost twenty years and only rented, and now have nothing to show for it.
WISE actually show you the comparisons with other traders. I transferred some money last week and they advised me that Western Union had a better rate. In the big picture it was only about 150 baht by the time it hit my Thai bank. Not worth the effort of opening new accounts etc. Actually when I did the transfer the following day WISE were back on top.