I recently moved from working in the Middle East to been retired in Thailand. My tax residence was previously Qatar and HSBC there had my TIN.
However when I moved and changed my permanent address to Thailand with my HSBC accounts in the UK and Hong Kong both banks required that I fill in a tax residence form again.
As advised from another reader on both forms under Thailand, TIN I simple wrote "Not Legally Required". This was after contacting both banks and explaining the situation regarding my status.
Both HSBC accounts are happy with this response.
Simple!!