Ask your hotel for a copy of your tm30 go to immigration to get a residence certificates ( need your tm30) once you have this then typically passport and one other form of ID then go try the banks, typically bangkok bank but I'm less familiar with pattaya. You should be good to go as you have a non o 90 day retirement visa. Go deposit 800k baht into the account and then after 2 months of the money being in your account apply for a 12 month extension
Your visa dates are the validity of the visa. You can enter on the last day and get your 90 stamp. The non O visa cannot be extended for 30 days, you can extend for 12 months but you would need to meet the extension requirements
I would suggest you look at the limited number of approved insurers mentioned on the e visa website as an example AXA are one of the approved insurers, you can get a quote online and they will provide you with the appropriate certificate for your visa
As Brandon has already mentioned there in no 12 month non O multi entry visa. However there is a non O-A visa that is multi entry for the first 12 months and can be extended 12 months as a single entry. This does have an insurance requirement from an approved insurance company as well as a police check and health check. You don't need money in a thai bank, it can be in your home bank, it still needs to have 800k baht equivalent or 65k baht monthly equivalent. If you plan to stay longer term it's easier getting a 90 day non o as Brandon has suggested