Police said the van hit the tree at about 11am on Sunday on Highway 41 in Sawi disrict, Chumphon, after the front left tyre burst causing the van to skid into the central reservation.
The van was totally wrecked as a result of the collision which killed four people on the spot and left 7 seriously injured. The injured were taken to Sawi and Thung Tako hospitals where two of them were later pronounced dead.
The van was hired, along with driver Det Juanchainart, to transport the 10 Marine Department officials from Phuket to Bangkok after they had completed their assignments on the island.
Pol Capt Manoch Plodkunngern of Sawee Police confirmed to The Phuket News that the six officials who died were identified as Mr Preecha Warojiem, 33; Mr Inthuram Poomsep, 59; Mr Samrueng Kaseasin, 59; Mr Kitti Siripongchantara, 47; Mr Chaiwat Sithikan, 42; and Mr Jaturong Saranai, 58.
The five injured are Mr Winai Jareonpum, 47; Mr Det Juanchainart, 59; Mr Surasuk Aumrapal, 55; Mr Chaiwut Arnunta, 42; and Mr Sombat Krasobthong, 49.