Six men died when two pickup trucks carrying seven collided in heavy rain in Surin province on Friday evening.
Five of the victims died at the scene while the other died at a hospital.
Police said the crash took place at 4.35pm between Km 166-167 on Chokchai-Dej-udom Road (Highway No. 24) in Kang-an subdistrict, Prasat district, Thairath Online reported on Saturday.
Police found a bronze-coloured Toyota Vigo truck with a Nakhon Ratchasima licence plate blocking traffic on the lane to Si Sa Ket, with the front crushed and the engine dislodged and landed on a road shoulder.
At the driver's seat they found Private Peerapol Kamin of the army's artillery centre. Beside him was Kongrit Prayong, 33, from Nang Rong district, Buri Ram province. In the back seat, they found Kanong Tip-aksorn, 40, also from Nang Rong. They were all dead apparently from the impact and cut wounds.
Rescue teams had to use steel cutters to remove the bodies.
Nearby, they found a blue Nissan Frontier truck with a Bangkok licence plate. The front was also crushed, all the glass windows were shattered and the fuel tank leaked.
They found Vichien Thongbai, 48, in the driver's seat and next to him was Nikom Thongbai, 62. Both were unconscious and seriously wounded. In the back seat, they found Prayoon Pimpan, 55, and Wilai Pachuen, 62, dead. All of them were from Khuang Nai district, Ubon Ratchathani province.
Police said the Toyota Vigo came from Si Sa Ket and was heading for Bangkok to send Pvt Peerapol to a training at the artillery school. The Nissan Frontier was from Buri Ram heading for Si Saket.
It remained unknown how the accident happened, police said.
The two survivors were sent to Surin Hospital where Mr Vichien died shortly after.