This thread in the Thailand sub-forum has some details.

Availability will be 100%, cost for flat-fare trip is published, and is 1,500 THB I think, exclusive of tolls. People seem to be paying 1,200 - 1,500 THB for a taxi ex-SBIA with tolls (less than 150 THB) being extra, these days. After you clear Immirgation, retrieve any bags, clear Customs, head straight out to (same level) the official metered taxi stand and inquire about the terms to Pattaya, make sure you understand the terms and tolls, and that the dispatcher and driver know your destination in Pattaya.

A mini-van, a la Bell Travel, would be 150 THB, while a private car service, a la Mr. T might be 1,500 THB all in. A moderate limo (Toyota Camry) might be 2,500, while the AoT limo service is closer to 3,000 THB.

http://wikitravel.org/en/Pattaya#Get_in

http://www.flyertalk.com/forum/archi.../t-664052.html

http://www.paradise-pattaya.com/pattaya-travel.html