I used my day to day account for my visa and extension with no problems except the statement was huge!! So I now opened another account just for day to day so I don't have to take an inch thick pile of paper to immigration lol
Why not fly to Thailand then get a Non O visa based on being over 50 then get yearly extension, there is no requirement for insurance just need 800,000 bath in bank 2 months before extending.
For health insurance have a look on Mr Prakan for all your Thailand insurance requirements
You can compare policies and prices in it from the leading providers