Taking the bus from Suvarnabhumi Airport
Just go to level 1 (same level as the taxi's) and then go to door (gate) #7 or #8. There are a few counters from bus companies.
There are buses (and mini-van's) going to/from : Pattaya, Jomtien, Hua Hin, Bangkok but also to/from Koh Samet, Koh Chang. And even to Khorat (Nakhon Ratchasima), Khon Kaen, Udon Thani and Nong Khai (border to Laos). Of course there is also a shuttle bus to/from Don Muang airport (DMK). They all have daily service, 7 days a week, but at limited times. See Airport Pattaya Bus or Bell Travel Service or Suvarnabhumi Airport Transport or Transport from Suvarnabhumi airport or Bangkok Airport