sounds like you are using a credit card to fund the transaction. If you use debit card or direct bank funding then it’s a flat fee. USD it’s $2.99 The only variable is the transfer rate and in USD it’s about .30-.60 baht per dollar less than the local exchange boxes advertised rates.
It is my understanding that using specifically Bangkok Bank you would be using their US routing number and your account number and this can be done in the online system. The change looks just like it’s a change to a US bank because of them using the US routing number for this NY branch. If not with Bangkok Bank then I am unsure of your path.
it was that same process for the first 90 day initial and then the 12 month initial. 1 day each time. I visited immigration for morning submission of documents and came back after lunch to pickup stamped passport.