What is the cause of the traffic jams?
I've only lived here seven months but the answer is obvious to me: Cars are a status symbol here. Every house on the cul-de-sac on which we live has at leasr one car inside the gate at night. Extra cars are parked on both sides of the alley at night until there is no room for more and barely room to drive thru.
And the odd thing is cars make no sense here. (Even my new Thai wife has reluctantly agreed with me.) Taxis are plentiful. We live close to a street on which taxis go by constantly. The nearest subway station is a 40 baht (US $1) ride away. The subway connects to the Sky Train. The two systems form a closed rectangle encompassing the center of the city. Anywhere we want to go is usually a 40 baht taxi ride from the station from which we detrain.
We avoid most traffic, parking problems (!) and the expense of buying and maintaining a car. Now if I could get my wife to agree to charging the neighbors for parking in front of our house, it would be a perfect world. (Perhaps if we rent the space inside our gate?)
A bonus in all of this is I get to view (wife permitting) some exquisitely beautiful Thai women who seem to be on every train we take.