FYI, we just arrived in the U.S. after a month in Thailand and 2 days in Hong Kong. Lots of Thai people wearing masks in the big cities. Maybe 40%, less so in smaller population areas. Hong Kong was a different story. The airport was a ghost town when we arrived as was our airport hotel. Almost everyone except hotel front desk staff and tourists were wearing masks which were nearly impossible to find. I's say 99%+ near the airport, downtown, and subways. When we explored in the new territories the number went down to probably 75% in areas where we were among the few obvious westerners. There were lots of people cleaning on subways, escalators, door knobs, elevator buttons etc. and everyone was thermal scanned at the airport on arrival and at our hotel restaurant. We finally started wearing masks that were given to us on a Bangkok Grand Palace tour because we felt out of place and a bit rude to be uncovered when all else were. The only question we were asked on arrival in Hong Kong and LHR was "have you been to mainland China in the last 14 days."
A new one for us leaving Chiang Mai direct to HKG. The AirAsia A320 had less than 40 people on it. Less than a bus full. Took a picture when the doors closed and the vast majority of the plane was empty. A couple of minutes after announcements and safety drill the pilot gets on the horn and notifies us that there's a "safety issue" and we need to swap planes. We'd already had our Bangkok to HKG flight cancelled and replaced with this one. Anyway we all got off the plane drove around the airport on the tarmac bus for 15/20 minutes and then got back on the SAME plane and had a great flight. DW speculated that they removed some fuel from the plane and that sounds pretty plausible to me.