The Sarika Travel agency van veered off Phetkasem Road and slammed into the stalls before coming to a halt after hitting a tree in Muang district, said Pol Lt Sathit Duangdee.
The vehicle with five passengers, a driver and a tourist guide was travelling from Bangkok to the diving destination of Koh Talu in Bang Saphan Noi district, he added.
The tourists were injured from the impact of the crash as they were sitting inside the passenger compartment. They were sent to the provincial hospital. Names have not been released.
Driver Kochanat Inthiharn was slightly hurt and guide Viricha Surasakpimolkul was unharmed.
Police suspect the driver had fallen asleep behind the wheel.
Uthaiwut Chimwiset said his shop and the sleeping quarters behind it were destroyed by the vehicle.
The shop owner said it could have been worse, as his daughter and son normally slept in the spot that the van hit. However, the two children left for Bangkok last week for school, he added.