The transport companies that will take you exotic destinations like for example down town Pattaya have launched an online website where you can book the ticket online.
As you already guessed the website is totally in Thai but if you lucky you can find the routes anyway with the time in English, even if they spell Chonburi – Chanburi.
I really do not know what the website it for maybe it is for routes that are not that trafficked but for Pattaya there is a bus every 20 min and I never had to wait longer then that. They now also made it possible to leave Pattaya as late as 23.30. If you want to go home before the wife wake up in Bangkok there is also a bus that leaves at 04.30.
Thailand Transport website and Busses to Pattaya