Hundreds of striking workers forced U.S. auto maker General Motors Co [GM.UL] to shut its Thai assembly plant on Monday, company and union officials said, raising the stakes in a pay dispute with management.

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 in 1999 with most of its output, mainly small pick-up trucks, exported to dozens of countries.

The strike has necessitated the temporary closure of General Motors Thailand's Rayong facilities to ensure the safety and security of all employees and property, GM said in a statement. The automaker, which emerged from bankruptcy in July, said it would attempt to reach a solution with the union as soon as possible.

(Reporting by Vithoon Amorn; Editing by Jason Szep)