Of course, since there are pax whose destination is HKG. You should let the crew or ground staff know so you don't delay the onwards flight to the detriment of other passengers as you are paged throughout the airport (your grandmother suddenly took ill in HKG.....)
Also, checked luggage would be an issue.

Finally, doing this would invalidate any subsequent sectors (eg if this were a BKK-HKG-ICN return).