I think that it's fair to say nobody knows for sure what is going on. It even seems to me like immigration officials themselves are making it up as they go.
Every school is different. If you get in with a good school, they will take care of it. Some schools don't really care. A good school should offer a 12 month contract from the start. But many schools now are trying to get away with paying only 10 months.
You should be okay. They're not really all that concerned about past Visa exempt entries. They are looking at extensions of Visa exempt entries. That's the key. You will likely get a few questions, a bit of a scolding, and told to get a Visa next time. By the time 'next time' comes around ; all these 'rules' will have changed.
The British pension amount will remain frozen at whatever it is the year that you enter Thailand. There will never be any cost of living increases. No big deal the first couple of years, but quite significant after 10+ years of living here.
I don't think that anyone can answer your question with any accuracy. Thailand immigration officials seem to be making it up as they go. It's maybe, could be, and sometimes for the answers. Be great to get some clarity, but so far, none is forthcoming.
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