The van was taking 19 Cambodian passengers from Rayong to Ban Laem border checkpoint in Phong Namron district when it crashed on Sukhumvit Road in tambon Thung Benja of Tha Mai district around 7.10am.
The van left the road on a curve and hit a tree, then the gas fuel cylinders exploded twice, causing a fire. Many passengers trapped inside the van were killed by the fire, Suchart Khwanchai, chief of rescue at Sawang Katanyu Foundation, said.
The rescue team delivered a total of 12 people to three hospitals, four of them in critical condition.
The police suspect the driver fell asleep at the wheel.