@Pete ******

define "assessable income"

If you stay over 180 days in a Thailand tax year (1 January to 31 December) you become tax resident, this means you NEED to pay taxes on income earned this tax year that you brought into Thailand this tax year (bank transfer into Thailand, cash withdrawn in Thailand, cash brought into Thailand, card payment in Thailand). However, if you did NOT remit any income earned this year into a Thai bank account (e.g. Bangkok Bank) via transfer or cash deposit, it will be hard to pay taxes on it because the tax officer won't understand or know what to do without bank statements. So if you want to pay taxes you have to remit your annual income into your Thai bank account, and the only reason you would want to do that is because you don't want to be taxed on this income by your home country. To avoid your home country taxing you on this income, you have to ask a R.O.22 "Certificate of Residency for Tax Purpose" / "Certificate of Residency for Double-Taxation avoidance" to your tax officer, after you have paid taxes in Thailand, so you can prove to your home country that you are Thailand tax resident in case of investigation. You would usually need to provide your bank statements and your proof of income (e.g. invoices).