I have 0 experience personally with this but I’ve of course spoken to many teachers and haven’t come across this in the ESL realm. Perhaps it’s more common in International schools.
You might try your question in some teacher specific groups too.
Visa’s are new every year. You’ll have to reapply and provide required evidence. There’s no limit of times, can be 30 years but probably a limit of one wife at a time for visa qualification. 🙂
Might want to look at language schools as well. Yes you would need to do the Non O marriage to a Thai and you have the option to add a WP or a Non B which can affect your stay in Thailand as you lose the visa extension if you quit/get let go but the same would happen on a marriage visa if you quit or were let go by the wife.