Another way of searching: RTs are often cheaper than a series of OWs, they often allow stopovers at the hub of the carrier. Open Jaw tickets are in a similar price range.

You could look at an open jaw BRU-XXX-NRT and return HKG-XXX-BRU in combination with One ways in Asia.
Another option could be a CX open jaw to NRT / back from SHA with a stopover in HKG.

You could also combine an RT or open jaw with some of the airpass offerings.

Without a lot of experience it is pretty difficult to find and also book these kind of tickets. A good travel agent is worth his fees for these kind of trips.