Hi,
If you are resident in the UK and you sell a property in Hong Kong, you will pay tax in Hong Kong on the disposal. You will also need to declare the disposal on a Self Assessment tax return, as you may also be liable to capital Gains Tax in the UK.
After using the official exchange rates in force at the time of acquisition and disposal, you would follow HMRC guidance to calculate if a gain arises. If it does, it is reported on SA108, capital gains, and SA106, foreign, where you can claim a foreign tax credit for any tax paid in Hong Kong on the disposal.
Capital Gains Tax
Tax on foreign income
Thank you.