Regulation - if you buy a condo, money need to transfer from overseas in foreign currency and exchange in Thai by bank, not wise and not Western union
(Not sure if this need for applying any visa )
Bring foreign currency by hand and exchange in Super Rich = best shop* exchange rate
Other way- use credit card
The ultimate best way- find an Thai gov accredited stock broker who accept your hometown currency , move the money there , then you get no spread of exchange rate ..(spread = same as the rate you check on internet) , before IB can do , now Thai bath is out