I used Wise yesterday to transfer the money from the UK, £'s to baht, for my visa app in December. Took 8 minutes from typing 'send' to arriving at SCB in Hua Hin. Wise will also show their rate versus other companies on their app (see pic). Most times they are the best and if they aren't it's usually an insignificant difference.
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.