A strike by workers at GM Thailand is reportedly costing the company THB200m (USD6m) a day.

Union leader Voravudh Potisoonthorn told the Bangkok Post that the production line, which has been shut since Monday, normally rolls out 160 pickup trucks each day.

"The negotiations between the union and the management have not shown any progress so far and we cannot foresee the end of it right now," Voravudh said.

He said around 700 unionised workers have gone on strike.

GM Thailand said the union's demands include incentive-based payments, company's support for union activities, and for the automaker to cover the costs and damages resulting from the strike.