I opened a Bangkok Bank on a 30 day visa waiver, 1st bank turned me down, 2nd gave me the account. People do it here all the time, Bangkok Bank is usually the go to. Recently there was a notice outside a K Bank in one of the malls that they were accepting foreigners on tourist visas.
But, these Facebook groups are always full of Westerners in denial because they are unable to do anything without an agent