We now know that offshore income earned in 2023 and earlier will not be subject to personal income taxation when brought into Thailand in 2024 or later.
One more link to confirm this:
https://www.lexology.com/library/detail.aspx?g=017cd161-512b-4f56-94d3-3f942a23fc4d
A hypothetical scenario: Let’s assume that a Thai tax resident has a foreign brokerage account and has bought Apple stock for $60,000 a few years ago. The value of that investment is now $100,000. It looks like it would make sense to sell the shares in 2023 to realise a non-taxable profit of $40,000. The whole amount can then be brought into Thailand in 2024 tax free. Correct?
If this investment is only sold in 2024 and remitted to Thailand, the profit of $40,000 would be taxable as capital gains in 2024.
Now let’s assume that the investment is sold in 2023 but the proceeds are left on a bank account abroad. The bank pays 4% interest and no withholding tax is deducted. For clarity, the account will not have any other transactions. By January 2025 the balance would have grown to $104,000, of which $100,000 is old capital from 2023 and $4,000 taxable income from 2024. A sum $100,000 is then remitted to Thailand, leaving $4,000 abroad.
Is this amount of $100,000 considered to be
a) entirely tax-free capital from 2023,
b) $96,000 tax-free capital from 2023 + $4,000 taxable interest income from 2024, or
c) 96.15% (100/104) tax-free capital and 3.85% (4/104) taxable income?