Quoting witnesses, Muang Phetchaburi police said the bus, chartered by a local Charoen Pokphand affiliate to transport its staff, overtook the slower trailer in the left lane and abruptly cut across it to make a U-turn near PP Park Intersection on a major road in Wiang tambon.

One of the witnesses, a passenger in the semi-trailer, said the truck was carrying a full load of bottled water and could not brake in time before it smashed into the middle of bus.

All eighteen people killed were passengers in the bus, and one of the six injured was the truck driver. There is no information yet as to whether the bus driver died, was injured, or fled the scene.