@John *********
Of course there are gains, unrealized gains because those investments have not been sold. I have also explained how this is managed so there can be unrealized gains for the total account and still not be liable for taxes on withdrawals.
For simplification purposes lets say this account starts with $100,000 of principle in it. I then buy $10,000 dollars worth of 10 different stocks, mutual funds, ETFs, etc with it. At some point during the year I sell one that has gained $1000 and is worth $11,000 at the time of sale. At another point in the year I sell one that lost $1000 and is only worth $9,000 at the time of sale. The net gain/loss for those two sales is zero therefore I owe no taxes on those sales according to US tax codes.
I now withdraw $10,000 of the $20,000 total in sales. The other $10,000 gets reinvested. At the end of the year all the investments still in the account are now back to being worth $100,000. But because I have not sold those investments there are no additional sales to be taxed beyond the two mentioned above, which resulted in a net gain/loss of zero. The net value of the account remains unchanged for the year despite withdrawing 10% of it.
Another way to look at it is simply kicking the capital gains taxes down the road to future tax years once those investments are sold. However as I've stated its a bit more complicated than that simplified version but should be more than sufficient to understand the concept.
I've also stated that thailand, like the US only taxes the gains on investments. What may possibly be different is it appears they do not allow you to offset gains of one investment with losses from another as the US does. I need to do more research to confirm this. Even if that is the case though it has zero impact on my original question.
In this scenario I am taking that $10,000 I withdrew from this account, of which it appears $1,000 of it would be taxable in Thailand, and combining it with another $10,000 from an account where the full $10,000 is taxable. I'm then taking $10,000 from this combined account and transfering it to Thailand. The other $10,000 I am using to pay bills in the US. I've now lost the ability to prove which source the money brought into thailand came from, and which source was used to pay bills in the US. This makes a difference because one would result in only the $1000 in gains being subjected to thailand taxes and the other the full $
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would be subjected to thailand taxes.
The simple solution, depending on how Thailand will treat this, is to stop combining these to sources of money and simply transfer directly from the account that has the lower tax liability.