I went to the first Bangkok Bank office i could find, while here on a tourist visa a few years ago and got my account. Just needed to show where I lived and my passport.
Still use that same account today.
I tried opening one at SCB too, since the BKK bank app was pure garbage before they updated it, but SCB branch I was at basically said "we won't help you if you don't deposit a million baht or have a work permit"