"Roughly how much would be the price?"
Could be more than the savings you get flying to this airport far from Bangkok!
Some of the transportation providers on this link can give you a price.
If Bangkok is the final destination flying directly there will save time. Bangkok has 2 airports, Don Muang and Suvarnabhumi. Pattaya is around 2 hours drive from Bangkok. U-Tapao is about 40 minutes from Pattaya.