I assume both of your bags fit the carry-on luggage limitations and you are flying CX or KA. There are a couple of notes:
* The airport may decide you cannot do that (by weight or size). In this case you may be able to get a tag from a CX/KA. That should work for HKIA (at least in the past) but I am uncertain about other airports.
* Even if you can get through security, some planes may not have enough overhead cabin space even in J. CX/KA may check your luggage in cabin.
* If you are connecting somewhere, there can be additional risks.

I would check one of them. I personally do not like to have too much carry-on as flights get delayed, canceled, or last minute gate change. It is just too much for me carrying two pieces of carry-ons.