I'm not a big fan of LCC's, but with Thai dropping a lot of flights because of the competition, either you fly them or accept pissing about at Swampy for hours after a long haul flight.
Never been impressed with Air Asia or their Thai offshoot, and I had shit experiences with Bangkok Airways when I first used them.
But since then I've used Bkk
Air a few times and can't really fault them.
I had nearly 40Kg of baggage on my last flight from CNX to BKK
, and even though I offered to pay, they didn't even charge me for it.