you don’t need to keep the 1.6 million in a Thai bank continuously, just for the 1st year extension of stay, then you can swap to the 65k monthly method for your second year and repatriate your funds back home to a high interest account. It works out a lot cheaper than your suggested option.
a Thai wife doesn’t need any visa to enter Thailand so by implication that they both need visas means they both need retirement visas and that the wife is not Thai.
Non-O: No insurance requirement, extension requires banked funds in a Thai bank account. Can live continuously inside Thailand without leaving with repeated 1 year extensions.
Non-OA: Health insurance and police records check. Only available from home country. Can use home country funds. Gives 1 year entry on every entry for the 12 month validity. Can get almost two years of stay out of the visa as long as you have health insurance coverage. After the two years you either extend in country with Thai banked funds and health insurance or you return to your home country and reapply with home country funds and health insurance.
Is your focus to live in Thailand or is your focus to keep your funds in your home country. That’s really what you need to decide.
both require banked money for in country extensions so really the only difference (other than the insurance)is the timing when you bank the funds. It really depends on what is your focus, are you going to be retiring full time in Thailand or are you going to be living long term but bouncing back home every couple of years.