The Photharam police station was alerted of the accident, which occurred in Ban Haad Samran village of Tambon Klong Takhod, at 1.15am.
The pickup was extracted from the canal and two bodies were found inside. They were later identified as Supoj Sondee, 45, and his girlfriend, Wanchaporn Chaimongkol, 21.
Their relatives told police that the two were driving to downtown Ratchaburi on an errand when the accident happened.