A pickup passenger was killed and 19 other people injured when a tour bus rear-ended a line of vehicles stopped at intersection traffic lights in Phon district of Khon Kaen early on Thursday.
Initial reports in Thai media put the number of injured at between 12 and 20.
The crash occurred around 12.30am at Phon Hospital intersection on Mittraphap Road, Pol Col Thanomsit Wongwicharn, chief of Phon police, said.
Police and rescuers arriving at the scene found an air-conditioned tour bus with Khon Kaen licence plates with its front stove in and five other damaged vehicles that had been waiting at the intersection lights - a crumpled pickup truck at the rear, two 10-wheel trucks, a van and a cargo truck.
A man identified only as Amnart, 53, was found dead in the passenger seat of the wrecked pickup. His 24-year-old son was in the driver's seat and badly injured.
Police said the bus was carrying teachers from schools in Sakon Nakhon province on a study trip to Rayong.
The bus driver, identified as Siripong Amnatrat, told police he was unable to brake in time to avoid hitting the vehicles waiting at the intersection lights.
Pol Lt Col Chanrophas Chaila, deputy investigation chief at Phon police station, said on Thursday afternoon that investigators were checking whether the tour bus was properly registered as a hire vehicle and had group insurance.
He said there were eight vehicles involved in the crash that claimed one life and injured 19 people. In addition to the pickup truck, the injured included passengers on the bus and in the van.
Teachers who sat in the front section of the tour bus were injured. The drivers of the pickup truck and the tour bus are among the 19 injured people.
Police were still looking into whether the bus suffered a brake failure or not. Hospital blood tests would show if the bus driver had been using drugs or alcohol, Pol Lt Col Chanrophas said.
The bus driver would be charged with reckless driving causing death, injuries and property damage, he said.
