PREY VENG, Cambodia — In the sun-baked flatlands of Cambodia, where dust stings the eyes and chokes the pores, there is a tiny clapboard house on cement stilts. It is home to three generations of runaway slaves. The man of the house, Sokha, recently returned after nearly two years in captivity. His home is just as he left it: barren with a few dirty pillows passing for furniture. Before his December escape, Sokha (a pseudonym) was the property of a deep-sea trawler captain. The 39-year-old Cambodian, his teenage son and two young nephews were purchased for roughly $650, he said, each through brokers promising under-the-table jobs in a fish cannery. There was no cannery. They were instead smuggled to a pier in neighboring Thailand, where they were shoved aboard a wooden vessel that motored into a lawless sea.