I've lived in Thailand for 10 years on OA long stay retirement visa for which I had to have TGIA approved health insurance. I already had a good health insurance but the company wasn't part of TGIA group. I went to Cambodia to void my OA visa and back same day. On return to Thailand I had 60 day visa exempt stamp. After 30 days I applied for and was given 90 day Non O visa. I needed to show 800,000 baht had been in a Thai bank for 3 months prior to my Non O application.I shall apply for Non O 1 year extension at the end of November on grounds of retirement.
Andy, has the process changed with regards affirmation? My experience is that as a British citizen you apply for an affirmation of freedom to marry. No ceremony, just submission of a document with divorce certificates of any previous marriages. When the affirmation is confirmed, it needs to be translated and notarised as an accurate translation at Chiang Watthana Thai Ministry of Foreign Affairs.
A TEFL qualification on it's own isn't enough to get a legal teaching job. Teachers need a minimum Bachelor degree to work in a government school. You might find a teaching job in a private school but I doubt if you'd get a work permit (with no degree). If the OP or spouse have a degree and get work, the husband/wife may be able to come as a dependent.
Definitely avoid OA because of health insurance. I've recently crossed into Cambodia without re-entry to nullify my OA visa. I got 60 days visa exempt then after 2 weeks applied for in country O extension. Passport stamped for additional 90 days. Towards the end of the 90 days I apply for 1 year based on retirement. I have to say Rayong Immigration were so helpful. No agents or under the table needed. I'll admit though, after everything was done I gave the 2 helpful officers some Ferrero Rochas and the general office staff a tin of biscuits for coffee break! 😁