@Mabel *********
To meet the requirements for a “retirement” visa you’d need to have 800k in a Thai bank in your name only. To get extensions off of that that would allow you to live here indefinitely would require 800k or international deposits of 65k every month for 12 months prior to application.
If you can’t meet that criteria financially then there are options but you’d need to speak with a specialised agent on what they could or couldn’t do for you.