HKG-BKK IS operated by FD, Thai Air Asia, NOT AK, which is Air Asia (Malaysia).
Search FT and you will find various experiences on FD. It is a decent airline. I flew it twice, and everything was fine. What "problem" are you referring to the carrier? Just keep in mind, you get what you pay for.
Air Asia is doing a promotion on HKG-BKK until May 16. From my experience, get the tickets immediately if the price is right. Cheap tickets will be gone in no time.