What paperwork do I need to open a bank account in Thailand on a retirement visa?

about to open one with Bangkok bank, they ask for my passport and a letter notorized by my embassy.

We opened ours a few months ago. We needed passports, 1000 baht per account (500 deposit and 500 for ATM card and first year fee) and a local phone number for each account. We went across the street to the 7-11 and got sim cards for 49 baht each. That was at a particular Krungsri branch. Another branch wanted stuff we couldn't obtain unless we had a bank account. Catch-22.

Letter from immigration that’s all

With a retirement visa, you will need your passport, and possibly nothing else. You could also need the things above plus a certification from your embassy that your passport is ligitimate, and, or, a letter notarizing your address. If you've done a 90 day report then you can get this address verification letter from immigration. If not then you get this notarized address letter from your embassy, but, depending on the bank, all you might need is just your passport with your retirement visa in it.

Roll of the dice.

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

You will need AT LEAST your passport, and a residency certificate from your immigration office or embassy.