An interesting post, Thaiga, and one that we can all relate to. I think CK made a major point when he said that the main reason keeping most of us here in LoS was our partners. Most of us are honorable' people, have married (or partnered) a Thai, maybe have children, support her and her family, have a house and/or land (almost certainly in her name) and came over here - or decided to stay here - in the expectation of seeing out our retirement in more pleasant surroundings than in our home countries. Many have 'sold up' at home for a number of reasons eg tax and as you say, we (Brits) are penalised as expats by our government.
But you ask if we would make the same decision (to come or stay) given the prevailing circumstances here regarding immigration, the exchange rate, Brexit (?) and so on. I suspect that for a lot of us the answer would be 'no', because as CK said, Thailand doesn't have a lot going for it these days as a retirement country given all the 'woes' already mentioned and there are other countries that are a lot more farang friendly.
In my case, I came here in 1997 when the Baht was still 38/£, but within a few months it had shot into the 80s due to the Asian financial crash. Three years later I retired, had been divorced for years, had grown up children, no property in the UK and more than enough to keep me occupied over here. The decision to retire here was easy; 6 years later I married a Thai and have been comfortably situated since then with house, land and a pleasant enough lifestyle. Until - that is - Thai Immigration started making waves for us by lumping us together with 'undesirables', because they are mentally unable to separate different parts of the same problem.
So, if I was working here now and was due to retire shortly, would I stay here? No, I wouldn't. I would return to the UK. But that is assuming I had no wife, still had property or assets in the UK and wasn't in my 70s! So - 'castles in Spain! As Ken says, a lot of are f*kced, because we have nothing to go back to and probably couldn't afford to live in UK now anyway. So we have no option but to make the best of it here. Let's just hope it all gets a bit better!