The exact circumstances of the tragedy were uncertain.
AFP said the pile-up occurred in Wang Chan district of Rayong province, 120 kilometres south-east of Bangkok, around dawn when a 10-wheel truck swerved and braked to avoid three elephants that had wandered on to the road.
A pickup truck slammed into the back of the 10-wheeler, killing two people and injuring two others, and an SUV swerved to avoid the pickup, crashing into one of the elephants, Police Captain Thanet Piumsorasak said, according to AFP.
The SUV then tumbled off the road and overturned, killing all four people in the car, including one Singaporean, Thanet said.
Pitak Yingyong, a forestry official, said the elephants were from the nearby Khao Anglunai Wildlife Reserve, and might have left the reserve in search of food.
“The elephant came down from the mountain where there’s drought so it was probably searching for food,” said police officer Teerawat Permwattanachaikul, according to Reuters.
“You can’t really see elephants at night because their color is so dim.”
The elephant, part of a group of three, was badly hurt and later died, Teerawat said.