Is switching from a Non-O visa based on age to a Thai citizen marriage visa advantageous due to reduced bank balance requirements?

Yes - but much more scrutiny

YES, But!!! I wonder sometimes, whether it is worth it with the mountains of paper work you have to produce for Immigration for this type of Visa.

AND if she divorces you the visa is invalid immediately upon divorce.

Check the requirements for your LOCAL office.

I have my own printer, and I have scans of my passport, pink border marriage certificate, Wife ID card, and House Register on laptop.

These I print and the other documents are printed when acquired.

Two sets are needed.

Pre-planning reduces stress.

Yes but the paper work home visits photos and so many other requirements are much more onerous

That is about the ONLY advantage in switching Non-O visa/extension from retirement to marriage based on banked money method. 😕

A marriage extension take a pile 'o paper, you also have to have the reason you're getting that extension (your thai wife) at the immigration office with you when you apply.

You only get a 30 day under consideration stamp when you apply for the year extension, then the immigration office can do a home visit (if they want to) and once that 30 days runs down you go back to get the year inked in

Compared to an extension based on retirement where you show up, apply, pay and get it inked into your passport that day (or at some offices by the very next day)

The choice is yours, but it's a decision you'd have to make and live with :)