I heard of this same issue at least 10 years ago when first looking into long term visas in Thailand, it's not anything new.
I personally walked into both KTB and BKB offices in downtown Pattaya and had no problem opening accounts in either bank holding a Non-O visa. Both printed and completed a US Government form upon activation of the account, and where seemingly very knowledgeable about dealing with US citizens.
This was 5 and 3 years ago respectively, but a friend of mine used a visa agent in Pattaya to assist with his retirement extension. They offered a lower cost to do that if he had an account with a certain bank, and accompanied him to the bank branch to set up the account. This was only a few months ago.
My suggestion would be to go to Bangkok or Pattaya, where there are more foreigners living and they're more familiar with the additional regulations. It's possibly easier to open an account in those locations. Or ask a visa agency for assistance.