The ATM fees are now up to 220 THB per withdrawal but with the Schwab card you needn't worry.

Living here, I stick to ATMs that are physically attached to banks or located within the confines of a shopping mall because ATM skimming isn't uncommon here. Unless it's an emergency, I would avoid standalone ATMs located near street corners or outside convenience stores.

As LIH Prem mentioned, always decline DCC and take the VISA/Mastercard rate.