I took the train, 2nd class sleeper, me downstairs , tilak upstairs, from BKK to Chiang Mai. I liked it cause it was different and it was a night trip so you dont miss out on anything. Not a bad way to go, but go by night. About 750 P.P. from memory.
Air, your 600 bht trip probably doesn't include taxes. Bkk to Phuket, or Udon or CM average around 1300-1500 all up. If you book in advance on the net sometimes its a little cheaper. Air Asia are often late so give yourself plenty of time if you book a connecting flight. And yes Thai are way overpriced. Nok and 12Go were both OK and no dramas. Careful with 12Go though, specially into a stormy Pooket.
