" . . . and I had to be at airport at 6am for 7:55am flight."
I almost never arrive more than an hour before departure time, sometimes a little less. But if you're not familiar with the check-in arrangements, you can waste a bit of time, especially if taking a budget airline with check-in in the other hall.
Or if OP doesn't have eChannel or an APEC card. Exit formalities can take a while at HKG. @:-)