@Nick ***********
you just didn't go to the correct branch of the bank. There is nothing in banking law that prohibits someone on a 30 day visa exempt or a 60 day tourist visa from opening an account, it's totally up to the bank manager at the branch you're trying, SO it would appear you're applying at the wrong branches :P
In Bangkok you can go to Krung Sri bank at Centra World, OR Kasikorn bank in Emquartier and open an account with just a passport and your address written on a piece of paper