Shortly after midnight, Thalang police and Kusoldharm rescue workers were called to the scene at Saladaeng junction on Thepkassatrri Rd.
Police found one of the male victims unconscious lying in a pool of blood, with injuries to his head and right leg.
The second victim was found sitting on the road, with a few scratches and bruises. Both victims were taken to Thalang Hospital.
Police took the damaged motorbike with the collapsing front wheel to the police station.
Police later learned that one of the victims, Somjai Tengsomboon, 18, died in hospital from head injuries.
Police made their way to Thalang Hospital and questioned the surviving victim, Sathaporn Wongwai, 35.
Sathaporn told police that he and the driver, Somjai, had been drinking in Maeng Mai. They were driving around looking for a new place to drink, when Somjai crashed the motorbike into the road sign at high impact.