If a farang lives in Thailand for more than 180 days in a tax year, he or she becomes tax resident in Thailand. Now the question is what if he wants to buy a thai condo and use money from overseas ? According to Thai Revenue website, overseas income is not tax in thailand unless it is brought into Thailand. I assume personal income tax need to be paid on this money or there is some kind of exception?

Just import the money from your savings rather than from your income.

"If a farang lives in Thailand for more than 180 days in a tax year, he or she becomes tax resident in Thailand. Now the question is what if he wants to buy a thai condo and use money from overseas ? According to Thai Revenue website, overseas income is not tax in thailand unless it is brought into Thailand. I assume personal income tax need to be paid on this money or there is some kind of exception?"

Interesting question actually.

This is my assumption, would be intersting to hear other views on this:

A: If you - in spite of the 180 days in Thailand - are also "domeciled" in another country (e.g. your country of citizenship), then one might assume that you have already paid tax on the money you talk about in that country, and through double taxation agreements, although you would be tax-liable in Thailand you would not have to pay any tax in Thailand on it in practice, assuming that the tax rate in your (other) country of domecile would be higher than that in Thailand. (This would be true for e.g most European countries.) . If you have not paid tax in your (other) country of domecile on that money, then you are likely tax-evading w.r.t. your (other) country of domecile, and you would need to pay in Thailand.

B: If you are not domeciled in any other country, then I guess you would be tax-liable in Thailand for that money.

On the other hand, theory is often far removed from practice, and in particular from enforcement possibilities.

(Note also that it is generally very difficult to "break away" from "home"-domecile for most European citizens, and of course for US citizens it is impossible. So I guess most TV members would fall into category A ... )

If you transfer money into Thailand to purchase a condo, why would you think of claiming it as "income". You simply SWIFT in money, not in that it's to purchase a condo. Pretty simple.