Three people were killed and five were injured when a family's pickup truck plunged down a cliff in Thailand.

Driver Jue Saeyang, 59, was taking his family to a market to buy school uniforms when he was said to have dozed off at the steering wheel.

The truck veered off the mountain road and rolled 100ft down a cliff in in Chiang Rai, on May 11. It then smashed into a tree in a lychee orchard, killing the three adults in the vehicle.

Police arrived at the scene after receiving a report from passing motorists, who saw the children crying in the cargo bed of the truck.

Officers found Jue's body crushed against the steering wheel. His wife, Yua Saeyang, 57, and another relative Suda Saemua, 33, were also found dead in the driver's cabin.

The children suffered minor injuries and were taken to the Thoeng Hospital for treatment. They were identified by officials as Worameth Saeyang, 14, Adisorn Saeyang, 13, Anawin Saeyang, 9, Walaitip Saeyang, 9, and Praewwa Saeyang, 9.

A police spokesman said: 'It was found that the driver had been exhausted after organising two consecutive funerals.

'He was taking his wife, children, grandchildren, and daughter-in-law to buy school uniforms at the market but he lost control of the vehicle.'

Police said they will further investigate the cause of the accident.

Thailand has one of the world's worst road safety records. Ministers have set the goal of reducing fatalities from 32.7 deaths per 100,000 people to 12 per 100,000 people by the year 2027.

However, a lack of road safety education in schools along with notoriously easy driving tests, police failures to enforce road laws, and chronic under-investment in infrastructure, all appear to hamper the efforts.