Can I apply for a Non-O visa based on marriage while on a METV in Thailand?

The way it works is you will apply to change your tourist visa to a 90 day Non-O visa based on marriage, then once you get that you will apply to get a yearly extension of stay based on marriage.

on any of the 60 day tourist visa entries you have you can go to the immigration office and apply for a 90 day Non-O visa based on marriage to a thai by meeting the financial requirements of 400K baht banked in a thai bank account in your name only or a notarized letter from your consulate stating you get 40K baht a month in income.

You'll also need other documentation too, I suggest going to your local immigration office and seeing what is required