Datapoints:

I used a Schwab ATM card at a BangkokBank ATM at BKK last month. 150B fee was disclosed and printed on ATM slip - Schwab reimbursed this automatically (US$4.50) at end of month with no action from me.

Also withdrew from an AEON ATM. No fee. Exchange rate for this transaction was US$1=33.22B. Moneychanger at BKK was buying US$1 at 32.99B on same day. oanda.com reports 32.78 sell on date in question.