The accident happened at 11.15pm on the southbound Rama II road in front of Rajabhat Suan Sunantha University in Tambon Bang Kaew, said Pol Capt Chaiyasri Pholdee, deputy inspector of Muang Samut Songkram police.
The tuk-tuk driver, Wanchai Korom drowned after his vehicle collapsed in the shallow ditch.
Chaiyasri said the accident might have been caused by him falling asleep behind the wheel.