General Motors Thailand is cutting 500 jobs from the current 3,000 as part of a strategic plan announced in late February to restructure its Thai operations.
The US-based company has begun a "voluntary separation programme" for its employees at the main office in Bangkok and two plants in Rayong, said managing director Marcos Purty.
General Motors on Feb 27 said it would cease production of its Chevrolet Sonic in Thailand by mid-year.
While GM will still sell cars such as the Cruze sedan in parts of Southeast Asia — an emerging-market battleground for global makers — it is shifting focus to push the "American heritage" of its SUVs and pickups such as the Trailblazer and Colorado.
The restructuring marks a retrenchment in Asia by the US car maker.
While business grows in China, the world's biggest car market, GM has struggled in other parts of its international operations unit, which does not include China.
At present, GM runs two plants at Rayong's Eastern Seaboard Industrial Estate with a combined investment of US$1.4 billion: one a vehicle assembly plant with annual production capacity of 180,000 units and the other a powertrain plant with annual production capacity of 120,000 units.
The vehicle plant makes four Chevrolet models: the Colorado, the Trailblazer, the Captiva SUV and the Cruze passenger car. All are shipped to nine markets including the Middle East, Vietnam, the Philippines, Malaysia and Oceania.
"The situation of GM's manufacturing is very productive because the company focuses not only on the domestic market but also overseas countries," Mr Purty said. "GM has to adjust itself for gearing up its export volume in the near future to offset sales in Thailand."
Mr Purty, also managing director of Chevrolet Sales Thailand, forecasts a domestic sales slump to 800,000-850,000 vehicles in 2015, down from last year's 881,832.
"I have not seen any huge uptick for the Thai market yet, and sales will be stable below 1 million vehicles per year," he said. "Chevrolet's performance will also get a negative impact from the overall market."
The company sold 25,700 Chevrolet-branded vehicles in Thailand last year, down 54% from 2013, with shipments numbering 34,873 vehicles, down 19%.