Drivers in Cambodia have a real problem with lanes.  Or more correctly, they have no problems with lanes because they don't even know they exist.  I am certain a good percentage of the driving population believes lanes are street decorations.  The rest of the driving population just ignores them.

Single lines, double yellow lines, oncoming traffic...so what?

Tuk-tuk drivers straddle the lanes, too

The driving practices are somewhat understandable if one takes into account two basic driving principles here: [1] a driver should never stop so if there is some obstacle in his lane, he just goes wherever there is an open space but keeps moving; and [2] people drive the way they walk.  Do you stay in lanes on the sidewalk?