Buses from Bangkok to Pattaya go from 5 am to 10 pm every hour. The ticket price is about 100 baht ($ 4). Express bus to Pattaya is about two hours. It comes out North Pattaya. This is a local bus service here, which is about 4 hours way and will take you to the outskirts of Pattaya to Sukhumvit street. These buses travel from the eastern bus terminal in Bangkok. Tickets can be bought here prior before departure. Now, how to get to the East Bus Station in Bangkok from Airport.
In the airport building down to the ground floor and find the Airport link. Get to the end station and transfer to Phayathai BTS (see pointers when exiting Airport link). Now go to the BTS station Ekkamai (Ekkamai). East Bus Station is located near the exit of the BTS. Pleasant journey!