I had never heard of a "bed bus" until I boarded one bound for Poipet, a small city on Cambodia's border with Thailand. After squeezing down an aisle that thin people have to walk sideways to fit through—two tiers of beds down each side—I soon discovered that the bunks were double-occupancy, meaning I had to share the last remaining 3.5-foot-wide by 5-foot-long bunk, all the way in the back of the bus, with another person for the 9-hour ride through the dark, bumpy night.