you are assuming less than 180 days in any calendar year in Thailand. If so, your original statement is rather academic. If you are over 180 days in Thailand then you become tax resident in both countries and the DTA states how various items are taxed. The age pension, as opposed to a work for the government type pension is taxable income in Thailand if the funds are remitted.
this is incorrect. Please check with a CPA. Andy as you are from Sydney you would know that Aussie age pension is assessable income in Australia and also in Thailand. Your income MAY be below the personal allowance for tax, and it may not especially if you have rental income for instance. To say, as a blanket statement, pensions are not taxed in Thailand is frankly just plain incorrect.