SWIFT is flat rate so (unlike Wise) larger amounts are lower cost. My monthly transfer used to average about $26 in fees from wise (small amounts like ฿70-฿100k). Large amounts like ฿800k would be excessive. It costs me flat rate of $15 to send via SWIFT regardless of amount. Always send in USD and I usually get near mid-market rate from Thai bank.
one of us missed the point of the post. The OP stated that he had to have visa money in the bank for several months BEFORE the bank would issue a letter. Bkk bank does freeze funds AFTER giving a letter.