Nok means bird in Thai and the airplane's of Nok Air really do look like a bird! For the first time I did fly Nok Air, just a short flight from Khon Kaen to Bangkok (and the next day back). Going to Bangkok it was a bit older airplane, but flying back we had a brand new airplane. The design of both airplanes is to get as much people in the plane as possible so you sit a bit tight. But for a short flight that is no problem, as they are much cheaper as Thai Airways (what is actually not much better seating).
Inflight service is simple with only a simple snack. Drinks are not free. The good thing with Nok Air is that you have 15 kg free check-in luggage (as with Air Asia that will cost you 300 Thai baht extra). All together a good and smooth flight and I will use them again (price depending). For more information see Nok Air.