United Airlines has San Francisco SFO to Hong Kong for $474-$479 round trip for travel departures January to May 2019 with many itineraries offering nonstop flights in both directions. There are sporadic low fare dates each month.
These tickets in United Economy K do not charge for checked bag.
United Airlines San Francisco SFO – Hong Kong HKG – San Francisco SFO (nonstop flights)
$473.93 round trip Mon March 11 – Wed March 20