Others said they were lied to about the true nature of the job until it was too late to escape. Physical violence, nonpayment of wages, and the withholding of food were among punishments meted out to workers who did not submit.
In one case, a Laotian man who traveled to Bangkok in search of work was recruited to work on a vessel. He was told the salary was good and that he would return to shore every 15 days. When he found out that he would have to work for two years before returning to shore, he refused to get on the boat and was severely beaten by the captain. After five months, the ship docked and he managed to escape.
Max Tunon of the ILO's TRIANGLE project, which aims to prevent exploitation of migrant workers in the Mekong region, said the organization would like to see Thailand adopt standards and protection measures that conform to ILO standards.
Thailand should require boat operators to maintain crew lists, to provide reliable payment of salaries and a written work contract in a language that the worker can understand, and to set minimum rest hours. The Thai government is setting up seven centers to oversee recruitment and training as well as registration of vessels, which Tunon called "a positive step as long as there is sufficient oversight of these centers."
There has been some international pressure to clean up the industry. The European Union enforces restrictions against the sale of seafood involving forced labor. The United States prohibits importation of goods produced by forced labor. But the strongest pressure for change in the industry may actually come from consumers themselves, the study said.
"There are already indications that consumers are increasingly putting pressure on such large distribution companies, demanding that they cut their ties to suppliers with links" to forced labor and human trafficking, the study said. A recent petition demanding Wal-Mart, the world's No. 1 retailer, adopt higher standards for purchasing seafood products collected 100,000 signatures.
But more must be done, especially to protect workers on "long-haul" boats that leave shore for six months or more, said Dr. Supang Chantavanich, director of the center at Chulalongkorn University that co-authored the study.
"When a boat goes very far," she said, "it is beyond the protection of the law."