You could take a bus, taxi or private car.
There are bus departures from the Ekkamai bus station to Pattaya every 30 minutes. Cost is ~ 125 baht (or slightly less) per person. The bus will drop you at the Pattaya North bus station. You'll need to then take a taxi, motorcy or baht bus to your hotel.
You can hail a taxi on the street and negotiate a flat fare to Pattaya. Typically this will be 1,000 - 1,200 baht, and the passenger will have to pay the tolls (200 baht or less).
You could arrange a private car for the journey. I usally pay 1,500 baht.
For the return, there are buses to Suvarnabhumi, or you could arrange a taxi or private car, for similar figures or less.
Since I usually accompany visitors I arrange a private car, but I have taken a taxi off the street and the bus, once or twice. It's a shortish trip, 2 hours or less. The problem with the bus is that you might get a local, which will make dozens of stops, and/or terminate short of Pattaya.