Police said the accident happened at about 11.40pm at the intersection of Ban Sang-Phanom Sarakham and Bang Nam Priew-Prachinburi roads in Moo 4 village in tambon Ban Sang, Ban Sang district.
The pickup carrying the workers was driven by Chamroen Somboon while Watchala Mala drove the other vehicle.
Chamroen told police he had been transporting the 20 workers to their homes in Muang Prachinburi after they picked watermelons in Saraburi province.
Chamroen said he approached the intersection without checking traffic on the other road because he expected no other vehicles to be on the road due to the late hour and he crashed into the pickup at full speed.