Here's my action plan. Maybe this is helpful to someone, or someone can point out mistakes. I am not in retirement age yet but live off investments abroad, so this change certainly affects me.
I have a portfolio of stocks from different countries. I now set up a new broker account and moved all my US stocks and ETFs there. Selling and buying back shares that have appreciated realised all capital gains so they will not be taxed later.
The main reason to have two accounts is that dividends from various countries have different withholding taxes. For example, the UK and Singapore are 0%. Those would be taxed when remitted to Thailand after 1.1.2024. That is why it is best to have separate accounts.
The US withholding tax for Thailand tax residents is 15%. I already have a Thai tax ID, which I have sent to my broker, so they apply the double tax agreement and withhold 15% tax from my US dividends.
Calculating Thai personal income rates using the progressive levels (5-35%), I see that the overall tax rate rises to roughly 15% at around 1.4 million baht. I plan to remit up to 1.4 million per year and use a withholding certificate from my broker to prove that I have already paid 15%. I expect to attach proof of the withholding tax paid and be able to claim it as a credit (The Revenue Department has promised they will amend the tax forms for this). That means there should be little or no Thai tax to pay.
What if 1.4 million baht is not enough in the future? Maybe I need to buy something expensive. Luckily, according to the latest order No. 162/2566, the new rules will not apply to income earned before 1.1.2024.
Before the end of this year, I will transfer some funds to a new offshore bank account that is ring-fenced for remittance purposes. In January, I will send some of that money to my Thai bank account, and as pre-2024 earnings it will not be taxed. So, I have some savings as a buffer. It is possible to remit that pre-2024 money later as well, but if the offshore account accrues any interest, that interest part would be taxable in Thailand. We do not yet know how such mixed funds will be treated.
(If I sent more money to my Thai account now, in December, it would be assessable income because I have earned it this year. That has always been the case, according to the old law. So I have to wait until 2024.)
My other broker account, with non-US stocks, will never be used to send anything to Thailand. I can use those funds when staying abroad. At this point, they will not be assessable income in Thailand. However, even that might change in the future. Therefore, it is best to sell (and buy back) those shares now as well to realise the capital gains before 2024.
Does this sound like a feasible plan? Have I missed anything?