Do all ATMs in Thailand charge a foreign-card fee, and can you avoid it?

Effectively yes. Thai bank machines commonly add a flat fee of around 220 THB per withdrawal on foreign-issued cards, on top of whatever your own bank charges. Being flat is the important part: five small withdrawals cost roughly five times what one large withdrawal costs. Being straight about the source, this figure comes from traveller reporting rather than an official Bank of Thailand consumer leaflet, so believe the number on the screen over any article. The dated write-up is here: https://meetlocale.com/guides/thailand-daily-budget One thing that is not a fee but acts like one: if the machine offers to charge you in your home currency, decline it. What did your machine actually show on screen, and which bank was it?