11 for people buying their first car and ends on December 31. The conditions limit vehicles to those made in Thailand, engines to 1,500cc and the price to Bt1 million.
The buyer has to own the vehicle for at least five years to receive an excise tax refund of up to Bt100,000, depending on the model.
The first-car scheme has given a big boost to the automobile industry, which suffered severely from last year's flood, with some assembly plants damaged, parts supply lines disrupted and output cut.
Pol Maj-General Piya Tawichai, commissioner of Traffic Police, said the congestion in the capital has been caused by several factors including the number of people travelling during rush hour, which now lasts for four hours from 6am-10am and again from 3pm-7pm.
"Everybody is heading downtown to work and to take their kids to school. This has caused terrible traffic in the main areas in the capital," he said.
There are also many construction projects that are now taking up lanes such as the Skytrain tracks and stations.
"We set up special traffic channels to drain traffic from streets," he said.
Wichian Jungrungreung, director-general of the Pollution Control Department, is one of the hundreds of thousands of traffic victims in Bangkok. He has to wake up at 5.40am and leave home very early to avoid the traffic jams.