The accident happened in a heavy rain on a curved section of Highway 4009 in Thung Luang sub-district of Wiang Sa district at about 3.30pm.
The collision involved an 18-wheel trailer truck, a brand-new Toyota Hilux Vigo pickup truck, a Honda City and a brand-new Mazda car. The dead and injured were traveling in the three smaller vehicles.
The driver of the truck fled the scene.
The victims were travelling from Phrasaeng district to Wiang Sa and the 18-wheeler was heading toward Phrasaeng. The accident occurred when the truck failed to negotiate the curve and its trailer smashed into the three smaller vehicles.
Four people in the pickup truck were killed instantly. They were identified as Prasert Chamnankit, 43, Suchada Chamnankit, 42, Veerasak Chamnankit, 21, and Saowalak Chamnankit, 24. They were from Sai Khueng sub-district in Phrasaeng.
Six other people were injured in the Honda and Mazda cars. They were identified as Miss Nitaya Luangphakee, 30, Mrs Jintana Churachawong, Samart Churachawong, Sayant Churachawong, Mrs Tongkarn Churachawong and Kornphat Tangsee, aged 3. The boy died of his injuries on the way to Wiang Sa Crown Prince Hospital.