Opening a bank account here is a bit of a catch 22 situation and definitely the most difficult part of the non o retirement visa process. After trying at several banks and branches of the same bank I managed to open one at Bangkok bank, but you need a letter from immigration to achieve this, if it is still possible. If not this would be worth paying an agent to arrange as I understand they charge about 3,000 baht for this service and you are not tied into anything for future years.
If you get the
*****
day tourist visa in advance before you travel, you have plenty of time to organise everything.
I believe a 6 month lease is required to obtain the non o visa, so you can also look around for a rental place in the first 60 days of your stay. Ensure that when you rent a place the contract has a copy of the owners ID card and their "blue book" proof of ownership of the property.
Good luck.