By Agence France-Presse
Thailand exports billions of dollars of farm products to western markets in poorly regulated industries heavily reliant on migrant labour from nearby Myanmar, Cambodia and Laos.
A chicken farm owned by the Thammakaset company in Lopburi province has been at the centre of disputes by Myanmar workers about grueling days, lack of overtime and confiscated documents.
It has hit back with multiple defamation suits, a criminal offence in Thailand, but has yet to win.
Still the company has filed fresh defamation charges against one of the former workers named Nan Win and prominent Thai activist Sutharee Wannasiri, who had shared on social media a 107-second video about the case produced by NGO Fortify Rights.
Fortify, where Sutharee worked at the time, urged the company and authorities to drop the complaint, which will reach court on December 3.
"These complaints are a form of judicial harassment and should be dropped immediately," said Amy Smith of Fortify.
The International Federation for Human Rights also condemned the lawsuit.
But Thammakaset owner Chanchai Pheamphon said he was forced to bring the suits to defend the name of his company from false allegations.
"For the past two years, everyone blamed me but they never did a proper investigation," he said, denying accusations of confiscating passports and making workers endure herculean shifts of more than 20 hours.
"From now on, you will see that more lawsuits will be filed against a series of so-called human rights defenders in Thailand who to me are actually (rights) violators," he warned, adding that attempts at negotiation had failed.
Betagro, a Thai food giant that sells to clients around the globe, has said it cut ties with the supplier farm after the initial abuse claims.
If convicted, both Sutharee and the Myanmar worker could face up to two years in prison and large fines.
Sutharee said she believed the lawsuit was an "intimidation tactic".
Activism is fraught with risk in Thailand where political and business elite frequently bring legal cases against critics.