Please be patient. Service is only being restored this week.
TG from 2 July, will fly to HKT from Zurich, Paris, Copenhagen, Frankfurt and London The LHR flight is Saturday & Tuesday. (It is via Bangkok)
WS (Thai Smile) is restarting HKT-HKG 4X weekly
Qatar Airways is back 4X a week to Doha.
Etihad is 3X a week.

The flights have to be "direct: or via a quarantine route bubble otherwise you have to do your 14 day required stay at airport of entry.
If you wish to use a ticket sold by BA then your most likely option is on Qatar, or take the BA flight to SIN and transfer there. Finnair services Thailand via a connection at ICN using OZ.
I am trying to suggest the One World partners, but *A has some of the better connections.