Sam Rainsy is currently on a visit to the US to build political support for his party, which holds 26 seats in the National Assembly.
The ILO estimated in 2007 an influx of 270,000 Cambodian job seekers entering the market each year.
The letters now appear to be part of a business dispute with four other foreign men, who were found to be no threat.
Mu Sochua said she would not pay the fine.
Two men were accused of incitement in an ongoing land dispute between villagers and a powerful ruling party senator.
It’s rare for a company to gain a land concession from the government and not have a conflict with the locals.
All three companies are owned by Ly Yong Phat, a powerful senator for the ruling Cambodian People’s Party.
In Cambodia scores of men have recounted stories of modern-day slavery on board Thai and Malaysian fishing vessels.
The delegation included three Khmer monks who had spent about one year in jail each in Vietnam.
More than 100 anti-trafficking authorities, diplomats and rights groups from across the region met to discuss issues around trafficking.
In 2009, Licadho received 155 reports from women who felt they’d been treated unfairly in their divorces.
The film, directed by American Bradley Cox, is currently touring festivals and is scheduled for wider release in the US later this year.