Police said that as the double-decker was descending downhill, it failed to negotiate a curve and skidded out of the road and rammed into a roadside tree and a roadside pavilion before it overturned.
Died at the scene of the accident was Mrs Maneerat Thongchan and 39 others who are mostly officials of Taksin Palace in Narathiwat. A police official however said he suspected slippery road surface was blamed for the accident.
Rescue teams from Narenthorn Centre in Songkhla were eventually dispatched to the scene to pick up the injured passengers, most of them women, and have them sent to Jana and Thepa district hospitals.
Later on, seven seriously injured passengers were to Hat Yai and Songkhla Nakharind hospitals for treatment.
Police said that the passengers who are mostly officials at Taksin Palace in Narathiwat were returning to Narathiwat from Bangkok where they attended a meeting when the accident occurred in Thepa district of Songkhla.