Police said the accident happened at a bridge on Ratraj Rangsan road in Phichit&rsquo;s Taphan Hin district. 
The trailer of an 18-wheel truck broke free while it was crossing the bridge. It hit a pickup truck, a motorcycle and another motorcycle with side cart before it ploughed into a roadside animal food shop. 
A motorcyclist, Sarawut Meethong, 20, was seriously injured and died on the way to hospital. 
The truck driver, Rod Panphet, 51, told police that he was driving at about 40 kilometres per hour and he did not know why the trailer disconnected from his vehicle.

Runaway trailer kills motorcyclist, crashes into Phichit shop

A trailer loaded with construction sand broke free from its truck engine and crashed into a pickup, two motorbikes and a roadside shop, fatally injuring a motorcyclist on Saturday afternoon.