I cannot book a Multi-City incl HKG-SIN with HKG as stopover. It returned as no flight available. Could be married segments because both the TPAC and the short Asian hop are available.

AS robot system said current wait time is 4 hrs. There is no call back option. I gave up.

Could I try to book the TPAC online then call AS in subsequent days when the current crunch is over, to add the HKG-SIN segment and still within the same award cost, not an additional award unlike US-HKG-AU the HKG-AU would be additional ?