not true. Promptpay is becoming open to other counties, as an example I can use my Singapore Bank account to and send to a thai promptpay, and there are no transfer fees, just the Singapore banks does the currency conversion and sends the amount in baht., same thing with Malaysia.
Not sure if stillnthe same but last time I went to the bank the day before got statement and letter next day went to immigration and they said I needed the bank statement with a transaction on the same day so had to go back to back and get new letter and new statement