Don't forget 20k Thai baht or equivalent in cash IVE NEVER been asked BUT it is a requirement ,ignore everyone who says they know more than Thai immigration
PEOPLE HAVE BEEN DENIED ENTRY BECAUSE THEY DONT HAVE THAT IN CASH
I opened mine 10 years ago more difficult now you should be ok with non o or oa visa ,proof of address,and probably a Thai national who will vouch for you
OR ANY NON TOURIST VISA
I opened my account with kasikorn but think it's pot luck who you talk to
Don't know what country you are from but I think your better to bring your own currency,maybe a small amount of baht for couple of days,DO NOT CHANGE THE MONEY IN THE AIRPORT (super Rich ) ok but think still shut,use one of the independent exchange booths for the best rates when you out and about
I opened one on a tourist visa for me it was because I was coming three times a year,I have family here,and KNEW I would need one in the future,but even 10 years ago it wasn't easy went in a few bank and my wife had to sign as guarentor