You report to Immigration if you are in Thailand a continuous 90 days. If you are outside Thailand you don’t report. The 90 day clock starts again when you return.
Exactly. If you buy when you are young and stay with the company then they will cover you until you are 99 years old. This couple is unlikely to be able to buy adequate income at their age. They should consider whether they can self insure.
I have Pacific Cross insurance. I needed to synchronize my insurance with my OA visa dates. They understand the situation and found a way to do this. The BOI wants you to have 10 months of insurance when they approve your application. Hopefully you can explain what you are trying to do to your insurance company and they can accommodate your request. If not then you are stuck doing something else.