i never take cash with me so always need to get it from an ATM when there and the standard charge has always been 220 Baht per cash withdrawal no matter what the amount (but i normally do 20,000 baht each time) and then my UK bank has charged a transaction fee of £1.50 per time.
I take it you get MasterCard mid market rates?
Regular banks seem to not give you a good exchange rate, and also charge a transaction fee.
I take cash, then fall back on Chase/Starling/Monzo. Chase has a £500 daily limit while the other two are really clown shows.
I happily squander money on things like ping pong balls at gogos, drinks for mamasans, etc. but get really upset if a bank tries to scam me off £5