First, I would stay away from the Revenue Dept. Wait and see if and how they are going to enforce this. May never happen.
If they want me they are going to have to drag me down there, kicking and screaming in protest. I cannot see how the Thai Revenue Dept has any right to tax foreign income. None of their business, I refuse to pay.
Thais have long kept two sets of account books. One of which gets shown to the Tax man.
Many Thais keep no records at all and simply give the tax man a brown envelope if he comes calling.
Have two bank accounts. One you show the tax office, which always stays within the max allowance. And another account for additional funds.
If all else fails, leave Thailand. Time we farang stood up and told em where to stuff it.