No one was injured on the bus, which was carrying tourists from Vietnam and other passengers, said Chieng Am, a provincial governor.
The bus was speeding to overtake another car when it crashed head-on into the oncoming van near a factory industrial zone in eastern Svay Rieng province, which is near the border with Vietnam, he said.
The overcrowded van was carrying more than 30 factory workers and was driving within the speed limit, he said.
The garment industry is Cambodia's biggest export earner, employing about 700,000 people in more than 700 garment and shoe factories. In 2014, the Southeast Asian country shipped more $5 billion worth of products to the United States and Europe.
Road accidents are a leading cause of death in Cambodia. According to report from Transport Ministry, more 2,000 people were killed in traffic accidents last year.
Related story
Passenger bus hits school van
