From my taxman, for an over 65 year old....first 190,000 is free, plus a 60k allowance, so there's 250k. After that 0 - 150k is at 0%, 150 - 300k is at 5%, 300 - 500k is at 10%, and so on.
So in my case I can have 400k before I pay any tax, then I have 80k @ 5% = 4000 baht.