I have been with UOB in Pattaya for over 15 years and know the assistant Manager very well . She told me they can't open a new Bank account for any foreigner without a long term visa . Instructions from head office .
Can't see any problem here . You may get asked a question or two at Immigration , but you are obviously a tourist and not attempting to live in Thailand on a tourist entry free stamp .
All OK for you to get free visa exemption. At the moment it is still 60 days , but it will go to 30 days in the near future but it hasn't been announced when .