sorry disagree, the need for marriage docs, possible notarizations, interviews, home visits etc.
Compared to just putting money in the bank and proof of residence I'd go on retirement first and then later go to marriage once family settled in country.
Do you have 800k baht to be deposited into a Thai account?
If so a non-o 90day visa based on retirement would be your easiest to obtain out of country and then apply for your extension when the money is seasoned.
A non-o based on being married to a Thai national is cheaper 400k but infinity more didficult to sort out.
Easier path is retirement non-o and later down the road change the reason of extension to marriage once you get a handle on everything needed.