If you have access to a personal car, as some of our long term volunteers do, driving works best for shorter trips of maybe 200 km or less. A farang can drive anywhere in Thailand, even in Bangkok, with the help of a standard GPS unit. If you have a Garmin unit, a map that shows from Bangkok to every dirt road in every village, along with every canal, river and lake is available from ESRI (www.esrith.com phone 02-266-9948). They are a bit pricey at $300, but they do work.
For longer trips, say more than 400 km, taking a bus is cheaper and more relaxing. You can read instead of drive, and although there are bus accidents in Thailand it is still probably safer than driving. Local transportation at your destination may be a problem, however. If your destination is Bangkok, then the bus looks really good. Most farangs, even with a GPS which will get you there, do not enjoy driving in Bangkok.