By Pipat Jongmeekwamsook
Police believe Thongpoon Chanachan fell asleep behind the wheel and died instantly in the collision.
He was taking the workers from Bangkok to renew their visa in Tak.
Rescue workers found the Toyota van with the wrecked front section stuck to the toppled tree when they arrived at the scene on Phaholyothin Highway (Khamphaeng Phetch-Tak) in Tambon Kosamphee Nakhon, at 4.30am.
Rescue workers had to use heavy equipment to extract two injured passengers from the wreckage. The other slightly injured passengers told police that they left Bangkok at 10.30pm on Wednesday to renew their visa in Tak's Mae Sot district. All the passengers were asleep when the crash happened.
Police initially suspect that the van driver dozed off behind wheel due to exhaustion from a long drive.