MOKPO, South Korea — Life as a salt-farm slave was so bad Kim Jong-seok sometimes fantasized about killing the owner who beat him daily. Freedom, he says, has been worse.In the year since police emancipated the severely mentally disabled man from the remote island farm where he had worked for eight years, Kim has lived in a grim homeless shelter, where he has been preyed upon and robbed by other residents. He has no friends, job training prospects or counseling, and feels confined and deeply bored.“I want to go back,” Kim, 41, said during a recent interview in the shelter near Mokpo, the southwestern mainland port that is the gateway to dozens of salt islands where a monthslong investigation by The Associated Press found that slavery still thrives, an open secret among locals. “I feel trapped here,” he said.Kim’s plight illustrates the continuing failure of one of Asia’s richest countries to help workers who have been enslaved on the farms — often people with mental or physical disabilities. Three other disabled ex-slaves also told the AP that they wanted to return to the salt farms because of their misery and sense of aimlessness in the crowded homeless shelters that officials placed them in. On the farms, they said, they at least had a fixed daily routine, a job they became skilled at and a sense of purpose. An official on Sinui, one of the salt-farming islands, confirms that at least one ex-slave has returned to a farm. Activists and officials suspect there are many more.