The accident happened at 8pm on Tuesday on the Phetkasem road in Moo 5 village in Tambon Kkokyang, said Pol Major Pairoj Chanachai, inspector of the Nua Klong police station.
The truck was driven by a retired policeman, Pol Senior Sgt-Major Prayad Jongrak, 60. His relatives, who were killed in the accident, were identified as Chansri Chanlohit, 57, Walatha Rakthai, 36, Dara Rakthai, 37, Kamlolsin Banthitsak, 1, and Chanram Khamlue, 58.
Pairoj said the truck entered the curve at high speed and lost control.
He said the man was taking his family to Krabi to have dinner with his children, who run a businesses in the downtown area, to celebrate Father’s Day.
Local residents said the curve was often the scene of accidents, with the latest being the most severe.