Phil Robertson, deputy director of Human Rights Watch's Asia division, criticized the trial, saying it would have a "chilling effect" on independent researchers probing the industry.Natural Fruit, "has decided to take a punitive approach rather than address the problems in their factory," he said. "This is all about trying to intimidate people who are prepared to investigate human rights abuses."Hall, 34, faces up to seven years in prison and a fine of up to US$10 million.There are four criminal and civil cases pending against Hall, whose passport was confiscated by Thai authorities as a condition of bail set in June. The first, which began Tuesday, relates to defamation charges for an interview on the subject he gave to Qatar-based Al-Jazeera television.Virat Piyapornpaiboon, the owner of Natural Fruit, told The Associated Press before the trial began that he was saddened by the allegations, which he again denied.Hall was optimistic. "I don't believe there is any evidence ... to show that what I did was malicious or in some way against the company," he said. "I did it for the benefit of the workers, so I am confident we will win the case."The trial comes after the United States earlier this year demoted Thailand to the lowest level in its annual rankings of governments' anti-human trafficking efforts, principally over its failures to do enough to stop abusive practices in the Thai seafood industry.The so-called "tier 3" rankings for Thailand means the country could face U.S. sanctions.Hall has worked in Thailand for years and is an outspoken activist on migrant issues. Millions of impoverished migrants, largely from Myanmar and Cambodia, have left their countries to work in Thailand. Some do not have legal papers, and many work low-skilled jobs for long hours at pay below their Thai counterparts. They typically lack health and social security benefits.The trial comes after a months-long crackdown on freedom of speech that followed a May 22 coup in which the country's elected government was overthrown. Thailand's military rulers have also silenced their once-thriving political opponents, threatening them with prosecution if they disturb the public order.Virat, Natural Fruit owner, is the brother of the secretary-general of the Democrat party, which had opposed the ousted government and is seen as allied to the coup leaders.