Also received. I am Australian, all Thai banks will be requesting this. Easy to fill out. If an Australian tax resident, even if retired and living in Thailand, with no Thai income no need to have TIN. Tick no for the US questions. As our Australian Information Commission says we don't have to provide our TFN (Australian tax file number) to overseas entities then you just tick "C" saying your country does not mandate disclosure of your home TIN / TFN.