This seems like a bulletproof loophole. There will probably be found other ways to get around the demand for taxation. The most obvious way to avoid taxation in Thailand, will be to spend as little money as possible in Thailand, compared to now, where we spend or save all your money in Thailand. I guess that this was not the governments intention with this law. I have already started paying for all my international purchases with my foreign credit card, in order to avoid taxation in Thailand.
I am from a country with a double taxation agreement with Thailand and my pension have already been taxed before I receive it. I wonder if I will be able to deduct the full already paid tax, when I transfer only a smaller amount of my pension to Thailand.