Thailand's economy expanded in the July-September quarter after contracting in the first half of the year, with gross domestic product rising 1.3 percent from the previous quarter.
The report said people spent less due to income and financial constraints such as higher household debt.
Car sales in Thailand dropped to 145,801 vehicles in the third quarter from 193,756 vehicles in the previous quarter.
The NESDB forecasts the Thai economy to grow 4.0-5.0 percent in 2014, thanks mainly to global economic recovery and investment under the government's flood prevention and infrastructure plans.
Compared with a year earlier, gross domestic product rose 2.7 percent in the third quarter, slowing from 2.9 percent in the previous quarter.