Marks on the road indicated that the unidentified man, who is believed to be 50 to 60 years old, had been hit and dragged for about 100 metres.
Police were alerted after a badly injured body was found on the Lampang-Denchai Vajiravudh Damnone road in Ban Pae Mai in Tambon Wang Ngern of Mae Tha district.
The man had no identification document.
The body was sent to the Lampang Hospital for a post mortem.
Police found a black mudguard with blood stains in the middle of the road at the scene.