you do realise many people in the UK over 50 ,who own their own house have a private or company pension and saved investments would be millionaires. I’m not planning to leave UK when I retire, but I do intend to spend the winter years in warmer climates. 
service charge on restaurant bills. You’ve obviously never travelled to the US Canada ,Oz most of Europe etc. Also what do you mean second most exodus of millionaires? Which country is the first most? Are your statements factual and evidence based or do you just make them up? I understand this is social media and people can just say what they want .
I don’t think he said the UK is a horrible place to live. I split my time between the UK and Thailand . The UK apart from the weather is a fantastic place to live .
The boy is 13 and he resides with you. That’s fine. At that age the family law courts in the UK (and I’m sure it’s anywhere) give a lot of attention to the child’s wishes on which parent he/she wishes to reside with. The boy will be 16 in less than three years. I would hope he has good contact with his mother also. So your Thai ex-wife lives in the UK and you are thinking of moving with the boy to Thailand? You would want to make sure you give your son the best upbringing and the best education wherever you live, whether it be the UK or Thailand.  (Your assets or prenuptial are irrelevant here.)