Book a hospital appointment, Muay Thai course , dental appointments etc . Where you book will provide the full details on what treatments you are having and course length. You will NEED to pay for this
Your pension is frozen the day you become full time resident in Thailand. They can claim back overpayments from you via deductions from future payments
If over 180 days you will classed as tax resident. It’s is possible that you will have to submit your tax return from your home country and use a tax credit from there to offset any tax due in Thailand. Tax due maybe based on worldwide income