A police investigation is underway to determine the owner of the stray buffalo, with initial suspicion falling on a nearby Thai cultural theme park.
The first vehicle, an illegal taxi carrying a German passenger from Phuket International Airport via Phuket City to Patong, crashed into the buffalo about 1.10am.
The German passenger was not injured and the fare is unknown.
With the buffalo dead or injured in the bypass road, a second vehicle crashed into the creature and flipped.
A third car then clipped the buffalo, shunting the animal into the central median ditch, preventing further crashes.
Two of the drivers required treatment for injuries. One was taken to Bangkok Hospital Phuket and the other to Phuket International Hospital.
Liability rests with the owner of the wandering buffalo. Phuket City police are continuing their inquiries.
The number of buffaloes left on Phuket is being reduced rapidly as the island rapidly becomes urbanised.
There was a time before motorised vehicles took over when buffaloes roamed free on Phuket.