Hello, I am Keith, one of the experts on Just Answer, and pleased to be able to help you with your question.
Firstly, when you left the UK did you complete a Form P85 and send it to HMRC of the Inland Revenue before the amalgamation? If you did not you should do so immediately. Fortunately there is no time limit as to its submission, it is available on the web and can be filed on line. On receipt you will be classified as non resident in the UK. Once so classified you can spend up to 90 days in the UK in any one tax year without breaching this status.
If you spend more than 180 days in Thailand in any one tax year you are liable to Thai Income Tax. The basics you can find here:
This Thai rule is rather similar to a large number of jurisdictions world wide regarding the application of Income Taxes. Remember you must be resident somewhere for taxation, you cannot swan around the globe and not be taxed anywhere. Tax avoidance is now the subject of general international interest and your bank is probably protecting its back against future or even current inquiries from various authorities.
I m sorry to have to advise you that you are going to have to put your house in order and pick an appropriate location having regard to your circumstances.
I am so sorry to have to rain on your parade.