I regret not having taken some pictures of Bangkok (or Siem Reap) traffic so I have borrowed the images. What is immediately is the color of the throng. See the taxi below, bright pink, and most of them were like that. The picture I regret most not being able to take was when I saw a Barbie pink city bus (emblazoned on the side with the Barbie 50th Anniversary). Oddly enough there does not seem to be one on the net (at least that I can find).
The traffic was the heaviest I have ever seen with all major arteries moving steadily but slowly. The mix of buses, trucks, motorcycles and cars moved more like fish than anything else with each lane change happening through a sort of back and forth negotiation and then somehow everyone knew who was supposed to go. Imagining that I just had not seen miscommunications I checked for dings and dents and saw none.
What was most disconcerting was how motorbikes wove in and around each vehicle sometimes with only the driver helmeted but behind him a young mother and two tiny children. Another time a driver sped past with a woman in evening dress sidesaddle behind him.
One day we were passing by the National Stadium and our taxi came to a standstill amidst traffic halted in all directions. It seemed we were waiting for some royal personage to get to their limousine and then for all the attendant vehicles to be able to leave in any direction they wished. Thailand is a place where everyone stands in the presence of royalty under pain of arrest (you do not even joke about these folks).
In general, Bangkok is well served. The Skytrain, an overhead fast speed metro line covers half the city with standard city buses the rest. Taxis are everywhere and cheap enough to pose a real alternative to public transportation. There are also tuktuks, mosstly gypsy cabs of a motorbike with two seats side by side behind, and on the river are ferries and other boats. All are inexpensive.