Eighteen people were rescued at the time, but 23 others were reported missing. One was found alive on Friday and another was found dead, according to provincial police chief General Chuon Narin.
It was not immediately clear where the boat had come from or what it was doing off the west coast of Cambodia. Authorities, however, said two Cambodians who were sailing on the boat abandoned it after an engine failed and fled in another boat which came to pick them up, leaving the passengers behind.
They were both arrested and are being questioned by police, authorities said.
In Beijing, Chinese Foreign Ministry spokesman Wang Wenbin told reporters that his government was in close communication with Cambodian authorities.
“We urge the Cambodian side to spare no effort to search for and rescue the missing and quickly find out what happened,” he said.
Cambodian authorities have sought help from private boat operators in the area, announcing a $500 reward for each passenger rescued.
Survivor Chengui Sheng told authorities there were 38 men and three women on board when the ship began to sink at 10:30 a.m. Thursday, provincial spokesman Kheang Phearom said.
Those rescued were taken to a nearby Cambodian naval base, he said.