Buses in Bangkok are plentiful and cheap, the regular bus fares are incredibly low. Air-conditioned buses and micro-buses are only fraction more expensive. A bus route map is always available at most hotels and bookshops.
At busy hours buses don't always stop at every bus stop, they just slow down and its up to you to get on or off. Also if they are unable to get over to the kerb, they won't, they will just drop people off in the middle of the street, so be prepared to get off when you think its your stop.
There are three types of buses, Micro-buses, air-conditioned and non- air-conditioned. Since the price difference is very little it's advisable to take the superior Micro-buses or the blue or orange/buff colored buses for they are all air-conditioned.
The Southern Bus Terminal, in the Pinklao area of Thonburi, close to the junction with Thanon Nakhon Chaisi. Provides services to all points south of the capital, including Nakhon Pathom, Kanchanaburi (for the Bridge over the River Kwai) Cha-Am, Hua Hin, Chumphon (for Ko Tao and Koh Samui), Surat Thani (for Ko Samui), Phuket and Krabi (for Ko Phi Phi and Ko Lanta), as well as departures for destinations all the ay south to the Malaysian border, including Phattalung, Hat Yai, Songkhla, Narathiwat, Yala, Trang and Sungai Kolok.
Services to the north and northeast use the new Northern Bus Terminal ( Mo Chit).
The Eastern Bus Terminal ( Sathaanii Ekamai), at Soi 63, Sukhumvit Road, serves eastern and many coastal destinations including Chon Buri, Sri Racha, Pattaya, Ban Phe (for Ko Samet), Chanthaburi, Rayong and Trat (for Ko Chang).