Unfortunately, Iago, you have the wrong end of the stick. Dragonair can only join DPA (Dragonair Pilot's Association). Both DPA and HKAOA are members of HKALPA which is a blanket organisation that is affiliated to IFALPA.
Separate entities entirely.
Choice of employer was given to all ASL pilots less than a year ago and now, having made your choice, you want to change the rules.
HKAOA never supported the formation of ASL and were against it always. It is now a dying company and will cease to exist soon.
It would be hard to claim that you were anything but aware of the situation when joining ASL. HKAOA couldn't and wouldn't stop you from joining a legally formed company. Now, we don't have to accept you into the fold.
Sleep bed your made you've now it. (Old Christmas puzzle!)
Compo