It's all about what is defined as "income" and what isn't. Wise tax advisors have mentioned that you need multiple bank accounts that keep the two apart as if you mix them up, then you are toast. So, gifts and inheritance are not taxable (Thai law is fairly generous on this as it favours the rich here) and most else is, but you have to prove it through having the transactions labelled "Inheritance" or "Estate distribution" plus copies of the death certificate, letter of probate, and letter from the executor of the will regarding transfer and how much etc. to present if asked any questions... depends on how large it is, I guess, to how much attention it attracts. Pretty much all else is income from salary to dividends to interest from investments, unless the double taxation agreement excempts it, but those differ depending on what country you come from.
