About 200 of 800 unionized workers at the plant in southeast Rayong province joined the strike, a GM spokeswoman said. The rest were asked to take paid holidays pending negotiations with union leaders, she added.

But GM union leader Suriya Pochairuak put the number of striking workers at about 700.

The GM plant, which has about 1,700 employees on its payroll, produces about 50,000 Chevrolet pick-up trucks, passenger sedans and special utility vehicles a year.

The $750 million plant started production