I cant offer too much advice as I am not on a retirement visa but I do have a Non O and health insurance currently isn't a requirement for it. Also I wouldn't worry too much about using the Thai banks. I opened up my account with KBank using my initial Non O and had no issues whatsoever. Most of the people, not all but most, who are having issues with the banks are people who opened accounts with banks when they weren't entitled to them and Bangkok Bank customers.
Glad it all went smoothly for you. Im just waiting on my extension being granted, hopefully get it any day now. You'll just have to drink beers tonight instead!
it's something I've never understood, I want people to take care of my property and I also don't want to be worrying about looking for tenants every 6 months to a year.
you have to hold out for a good contract, as a renter you can be taken advantage of very easily, especially when you are responsible for repairs and decorations