Pol Captain Natthasit Thongcharoenporn, deputy inspector of Bang Na police station, said the accident happened at 8.30 am at kilometre marker No 2. 
The pickup was transporting 12 workers to a construction site when it lost control and grazed two cars before it overturned in the right-hand lane. 
The pickup driver and 12 workers were severely injured and they were rushed to the Piyamin Hospital. The drivers of the two other cars were slightly injured. 
Natthasit said police would check CCTV footage before deciding whether to charge the pickup driver.

15 hurt in crash on Bang Na-Trat highway

A speeding pickup truck overturned on the inbound Bang Na-Trat highway in Bang Na district on Saturday morning after it hit two cars, causing 15 injuries, police said.