@Rafael ********
As a added note, when you apply for the Non-OA, you can use a non-Thai insurance, provided it fulfills a set of requirements.
So you can get yourself a solid insurance, and simply get a new Non-OA every 2 years instead of extending in Thailand.
You can apparently even self-insure if you get denied by insurance companies, provided you have enough money saved up.
But extending in Thailand does as far as I know, require a Thai-based insurance.
They seem to want to go home every year, so might as well go the Non-OA route.