Pol Major Boonsong Upatham, inspector of Muang Kamphaengphet Police Station, said nobody saw the accident but passers-by found the bodies on the road at 10.30pm.
Boonsong said the two motorcycles apparently crashed head-on in the middle of the rural road, which had no lighting, in Moo 13 village in tambon Angthong.
The impact of the crash caused parts of the motorcycles to be scattered over the road.
The body of Prasit Phansuwan, 27, was found over his motorcycle.
The bodies of Ratchaphum Meemak, 19 and his wife, Piyamas Sukchuen, 25, were found beside their motorcycle.
Boonsong said the couple were apparently riding out of the village and the other motorcycle was coming the other way.