The driver told police the brakes failed as the bus made the steep descent into Patong.
Lt Col Maj Pattapee Srichai and fellow officers from the Patong Police arrived at the scene, in front of Wat Suwankhiriwong (Wat Patong), at 7:36pm.
The white Mercedes-Benz bus, registered in Nakhon Ratchasima, rammed into the back of a white Toyota Fortuner, reported Col Pattapee.
The Fortuner was then pummeled into a bronze Isuzu, causing an end-to-end chain reaction of one car being shunted into the back of another, he explained.
Among the other cars damaged in the accident were another Isuzu pickup, a Toyota Altis and a Honda Jazz, he added.
Rescue workers and ambulances from Patong Hospital also quickly arrived at the scene, and reported that only five people had sustained minor injuries in the pile-up.
Officers took an hour to clear the damaged vehicles from the scene amid heavy traffic, which included long tailbacks all the way back over the hills to Kathu.
The bus, operated by Ningbo Yonglin Travel Co Ltd, was carrying 30 Chinese tourists and three guides from a restaurant near Chalong Bay Pier back to the Bauman Residence Hotel, in Sai Kaew Rd, when the accident happened, reported police.
Officers have yet to conclude their investigation into the claims of brake failure and have yet to press any charges against the bus driver for the accident.