The accident happened at 3.40am on Highway No 24 (Chokechai-Dejudom) in Tambon Sakad.
The driver of the Bangkok-Si Sa Ket double-deck bus, Pradit Sopanawet, and the driver of the truck, Tawan Pannao, were both killed.
Six men and four women, not yet identified, died at the scene while the 11th victim died at Sangkha district hospital, police said. Of the 28 casualties from the crash, seven have serious injuries and were sent to Surin Central Hospital.
An initial police investigation found that the bus driver |was attempting to overtake a vehicle when he cut into the lane of the truck heading to Nakhon Ratchasima and crashed with it.