I got onto Pacific Airlines by accident - was trawling through the Jetstar website and when I chose Bangkok as Origin and HCM as destination, I was automatically redirected to the Pacific webpage which opened up with my chosen flights.
I'm having a bit of trouble getting onto the Pacific site tonight but can still access it via the Jetstar site - so I guess this is the best thing to do if you want to check availability and prices.
However I've just entered a few random dates and the fare is $120 USD and that's one way (!!) so a lot steeper than Air Asia.