I assume you are already on a Non-O 90 day retirement visa so you will be applying for the one year extension which is not a new visa. You will not lose any days.
You cannot get an extension without the 800k so it gets you up to two years with one border bounce (and new insurance) then you leave and start again with a new Non-OA from "home"
Do it online in the period of 15 to 7 days before your due date. If this is rejected you have two weeks to go in person (up to 7 days after the due date). If you haven't left the country then you should not have to report in person as this is not your "first" report in country, it is the first in a new assress/province.
You appear to qualify for Non-Immigrant Type “O” Retirement (over 50) or Non-Immigrant Type “O” Marriage (Thai wife) so the choice is yours. On a Non-O visa you can get a 150 day return ticket and get no issues with your airline or at Immigration.