You can take a taxi directly Pattaya/Na Jomtien. Go to the taxi desk outside the airport and then negotiate with the taxi drivers. The trip should take no more than 2 hours. Unless like us your taxi breaks down, which turned our 2 hour journey into a 4 hour one or take free transfer to Suvarnabhumi Airport and bus from Suvarnabhumi Airport to Pattaya/Jomtien. The journey between the two airport takes around 50 minutes. Just remember it is not possible to take the free shuttle between airports if you do not have a boarding pass for an outbound flight at the destination airport.