In the US there the Pilot Records Improvement Act mandates checks a number of federal databases and requires previous carriers to provide records.
If you work for an overseas airline, those FAA requirements need not be complied with, so if you had a DUI on the federal database, it might disqualify you from a job in the US, but not in HKG. Meanwhile while you work for an overseas airline, the time goes on and your old FAA get expunged after a period of time and are no longer reported under a Pilot Records Improvement Act process.
To my knowledge, PRIA is for checkride records. It came into being after a Colgan skipper with literally a dozen checkride failures stalled a Dash 8 into some houses in upstate New York.
You still need to get an FBI check done, and list any conviction, expunged or otherwise. They still show on an FBI check, but show as expunged.