Utapao is a military airport that bkk airways uses to fly from Pattaya to Phuket. I did fly the same route you ask 10days ago..I didn't want in the trouble to hire a taxi from pattya to bkk and then fly bkk-phuket..more time and money..so no for me..of course the problem with utapao is that it is a bit far from pattaya and taxi drivers might try to steal you..watch out..i paid 500bht and still thing was not cheap..anyway it is like 40-50minutes to go there so be there on time. check the web site for fares. you can get a web promotion and even if you fell asleep with a teerak in pattaya you can still call and re-arrange the flight
have a nice trip.