The accident occurred at about 6:46am at a U-turn near Baan Pa Khlok on the Pa Khlok-Heroines Monument Rd (Route 4027).
CCTV footage of the incident shows a white Suzuki Swift sedan speeding off course and slamming into a motorcycle as the rider was about to set off.
The impact crushed both the rider and the bike beneath the car before the vehicle continued forward into a roadside grocery store.
According to Thalang Police, the incident was first reported via the police radio centre at about 6:30am. Pol Lt Anusasan Klin Khiao, Deputy Inspector (Investigation) at Thalang Police Station, responded to the scene along with rescue workers from Pa Khlok Municipality.
Officers found four damaged motorcycles scattered at the scene and a white Suzuki Swift, registered in Phuket, with heavy front-end damage embedded in the shopfront.
The driver, identified as Saijai Raden, told police she had been working as a ride-hailing driver and had just dropped off a passenger at Phuket International Airport before heading home to Pa Khlok.
She admitted she had been driving passengers both day and night and had dozed off at the wheel upon reaching the accident site, causing her to lose control of the vehicle.
Police confirmed that the car first struck a motorcycle before veering into several other parked bikes and ultimately crashing into the shop.
One of the victims, Rujirada Intharit, 51, suffered severe injuries, including a severed left leg. Emergency responders rushed her to Vachira Phuket Hospital for urgent treatment.
The crash also caused damage to the grocery store owned by Sirirat Sonsiri, as well as to several other motorcycles parked at the roadside.
Investigators determined that the accident was caused solely by the negligence of the driver, who was fatigued and unable to maintain control of the vehicle.
Legal proceedings are now underway, police said.