Transport in Cambodia is rarely comfortable, though between the main cities there are big buses and tourist minivans that are more reliable and spacious than the utterly cramped and stinking local transport. Generally, the public transport system is bad, but functional. To far-flung areas, pickup trucks are often the way to go. These are packed to the very brim, and travelers are stuffed inside with barely enough room to turn their feet.
Within the cities, having a bicycle is the best way to go for those willing to pedal around, though it’s best to wait until you have some concept of the flow of traffic. Otherwise, motodops and tuk-tuks are everywhere, and they will make sure you know it. Walking almost anywhere in the country is an invitation for someone to come up behind you, often beep, and yell in your face, “MOTORBIKE!?!”
Traffic in Cambodia is insane, and to the new visitor complete anarchy. In a sense, this is true. Any vehicle can go anywhere it wants. Motorbikes don’t even seem to count as vehicles, as they scream around turns and rush full speed into oncoming traffic. Generally, the bigger the vehicle (and the richer the driver) the less he will care about the rights of everyone else. This is generally the policy anywhere in Cambodia, “every man for himself.”
Of course you can always surf the trains, too.