let's say someone send 20-30.000 to a Thai girlfriend from abroad. SHE will be taxed, because she has not been taxed before.
Or a pensioner who has a big sum in home country and transfers 100.000 every month. How can he prove that the money has already been taxed.
But truth is, no body know how they will enforce it.
I would have to part with 35% of my salary, if I stayed 180 days, so I choose not to. I can rent an apartment for 12 month in neighboring countries for that. If I pay tax, I get absolutely nothing in return.
And if I pay tax, I bet I will still have to pay the new tourist tax, they still talk about. On every entry.