I have the government pension from the UK, a private pension, and income from property. At the moment I put these directly into my HSBC bank account and transfer randomly. Going forward, should I get these paid directly into my Thai bank account? This may avoid me having to put them through the UK tax system. However, by putting them through the UK tax system, I get a better personal allowance.

You cannot avoid or change the jurisdiction you want to be taxed if you are a Thai tax resident, and you have overseas assets. For example, a UK pensioner cannot easily get an NT tax code while being a Thai tax resident, meaning tax will usually be deducted at the source in the UK. If you then transfer funds into Thailand, it’s taxable, but you can potentially use any tax paid as a credit against taxes owed in Thailand.