The chain-reaction crash occurred at about 1:30pm on Kata Noi Rd, Karon Police reported.
According to police, and as recorded on CCTV, the cement mixer truck, registered in Phuket, was descending the steep road from Rawai into Kata Noi when it slammed into the rear of a green electric taxi, also registered in Phuket, that was waiting for traffic to pass.
The force of the impact pushed the taxi into a Haad Thip soft drink delivery truck, registered in Songkhla, which was travelling across the intersection, towards Kata Noi Beach.
The runaway cement mixer truck also hit the back of the soft drink truck as it sped uncontrolled through the intersection, but somehow not hitting any passing motorbikes.
The cement truck came to a halt only after ploughing into a wall at the bottom of the hill.
Karon Police, rescue workers from the Kusoldharm Phuket Foundation and ambulances from Chalong Hospital rushed to the scene to assist the injured and clear the road.
Police identified the cement mixer driver as Alisol Langyanai.
The driver of the EV taxi, Mr Sampan Kaewchang, sustained serious injuries and was transported to Chalong Hospital for treatment. Another injured person, Ms Bang-on Suriyong, an employee at a nearby massage shop, suffered minor injuries.
Police also noted that the crash caused damage to vehicles at the scene and to the nearby Red Lobster restaurant, where the cement truck came to a halt.
Karon Police investigators, led by Pol Lt Col. Narutphon Kaewlae, are continuing their investigation into the cause of the crash.
Initial findings indicate the cement truck may have suffered brake failure while descending the hill, though officers are also examining whether reckless driving contributed to the incident.
Karon Police chief Pol Col Pathapi Srichai confirmed that further legal proceedings and technical inspections of the truck will follow.