If you want to go to Suvarnabhumi Airport from Pattaya by bus, there are basically two options. The first one is Bell Travel Service, the second one is Pattaya Airport Bus Service.
Bell Travel Bus Service
The bus terminal of Bell Travel Service is at Pattaya North Road, just same location of Roong Reuang Coach (Going to bangkok). Their van can pick you up at your hotel based on web booking, not only to go ther bus terminal directly.
>> Go to Bell Travel Bus Service
Pattaya Airport Bus Service
The bus terminal of Pattaya Airport Bus Service is located at Jomtein at Theppraya Road just close to clossroad between Theppraya Road and Thep Prasit Road. Advance booking is valid for three days before departure.
>> Go to Pattaya Airport Bus Service