The accident took place near the Buri Ram government complex.
One of the passengers sitting in the flatbed of the truck reportedly flew out from the impact and landed in the ditch first before the truck landed on him. It took rescuers 20 minutes to pull out his body and rush him to Buri Ram Central Hospital, where he succumbed to injuries.
The rest of the passengers and driver all sustained injuries, including two toddlers under two years old.
Fongchan Trakarndee, 57, one of the family members said she and her relatives were travelling from Samut Prakan to the Northeast province of Surin to cast their votes.
After interviewing witnesses, police said they suspected the driver fell asleep due to exhaustion after driving all night.