The collision occurred at about 10:44am on Soi Loarong off Pattana Rd in Talad Nuea, Phuket Town.
Police and rescue workers arriving at the scene found a white Toyota Yaris bearing Bangkok licence plates and a damaged saleng along with two other vehicles that had also been struck in the incident.
The injured vendor, 56-year-old Wannaporn Siangaek, suffered a broken leg and was provided emergency treatment at the scene before being transported to Vachira Phuket Hospital.
Phuket City Police Chief Pol Col Chatree Chukaew said investigators found that the Yaris was travelling against the flow of traffic before colliding with the saleng.
A dashcam video recorded by a black sedan involved in the crash later surfaced online, showing the Yaris driving the wrong way before crashing head-on into the sidecart motorcycle, startling other motorists in the area.
Police confirmed that four vehicles were damaged in the incident: the Toyota Yaris, the motorcycle sidecar and two other cars.
Initial investigations found that the Yaris was being driven by a man identified only as Nattee. Police believe he was travelling at speed when he lost control of the vehicle, causing it to veer into the motorcycle lane and crash into Ms Wannaporn’s samlor before striking other vehicles.
Pol Col Chatree said the driver told officers during questioning that he had stepped on the accelerator and the vehicle suddenly lurched forward, causing him to lose control.
Alcohol and drug tests conducted on the driver returned negative results, police confirmed.
Pol Col Chatree said investigators have not yet determined the exact cause of the crash and are continuing to gather evidence. Officers are examining whether mobile phone use, an overtaking manoeuvre or other factors may have contributed to the collision.
A preliminary charge of reckless driving has already been filed against the driver while the investigation continues.
Police said further legal action would depend on the findings of the ongoing inquiry.