It's not quite what you're looking for, but what I usually do is to pull up the local airport's Wikipedia page which almost always lists airlines and destinations to pick out likely candidates.

http://en.wikipedia.org/wiki/VHHH#Ai...d_destinations

One thing to keep in mind in HKG is that quite a bit of the LCC traffic goes through Macau instead:

http://en.wikipedia.org/wiki/Macau_I...d_destinations

In Hong Kong you can often get very cheap fares to BKK on random airlines that fly XXX-BKK-HKG or XXX-HKG-BKK and discount the tag-on leg to fill seats. These include:

Royal Jordanian
Ethiopian
China Airlines (of Taiwan)
Kenya Airways
Emirates
Sri Lankan

With the exception of China Airlines these flights are not daily though, so shop around and be flexible.