The smash in Samut Sakhon province near Bangkok occurred when a six-wheel truck slowed down to pick up workers and was hit by a 10 wheel lorry that tipped it over, police spokesman Lieutenant Colonel Chaipat Charoenwai said.

Seven people were killed in the collision.

"There were people waiting at the roadside. That's why there were so many people dead and injured," Chaipat said.

Soon afterwards, two trucks on the other side of the road collided after one slowed down to look at the first accident, leaving two more dead.

In total 66 people were injured in the two crashes, with three in intensive care, he said.

Seven of the dead and 65 of the injured were migrant workers, reportedly from Myanmar, who were employed at a local seafood supplier.