More than 100 students and villagers crowded into a northeast Thailand college forum to hear about American gas companies conducting drilling operations in their region. A lieutenant colonel and dozens of soldiers and police officers followed them in.

The armed police began photographing members of the crowd, a menacing move in a country now run by a military junta that bars protests and routinely cracks down on dissenters. Some in the audience had already viewed the military as part of the problem, since months earlier they had forced demonstrators to make way for drilling equipment.

"With soldiers in the meeting room we were scared because we could not criticize the state officers who protect the company," said Chainarong Sretthachau, a professor who organized the May event at Mahasarakham University. "If I did not agree, they would not allow us to organize the conference."

Villagers in the northeast provinces of Udon Thani, Khon Kaen and Kalasin are trying to stop the drilling operations by American company APICO and its subsidiary Tatex Thailand.

Opponents of the operations describe them as fracking, or hydraulic fracturing. The technique requires high-pressure injection of water, chemicals and sand to crack shale rock and allow gas to seep out, but has been criticized for causing water pollution and even triggering small earthquakes. Fracking has boosted fuel production in the U.S. and elsewhere while meeting increasing opposition from affected communities.

APICO has said it is not fracking in the Southeast Asian country, though documents relating to its work say fracking was at least attempted there and describe wastewater ponds that are consistent with fracking operations. The Thai government says fracking is going on in the country's shale-rich northeast but would not say precisely where.

In any case, the drilling will apparently continue. Earlier this year, Thailand's Office of the Ombudsman dismissed a complaint that the country's National Human Rights Commission had filed on the villagers' behalf. The ombudsman's office, which investigates allegations of government wrongdoing and can refer cases to Thai courts, did not return phone calls or emails and provided no explanation for the dismissal.

More than 200 residents in communities near well sites have complained to the human rights commission about skin and respiratory problems and six have been hospitalized, according to commission member Nirun Pitakwatchara. Videos of farmland posted to Facebook and other sites allege that rubber trees and other agriculture have been damaged by associated airborne chemicals such as sulfur dioxide and hydrogen sulfide gases. Chainarong said that locals in one village near a gas operation report that their water has become brown and unusable.

Phuthon Anochadech, a villager whose rubber trees are near APICO's operation in Udon Thani, said that when drilling began two years ago, "It smelled so bad, we couldn't breathe."

He said in a telephone interview that he lost nearly 1 million baht ($28,000) that year because his trees produced little, and his worker quit because the fracking work was making him sick.

"Before all this, he was a healthy man, but during that time, he had to take allergy pills every day, his eyes were always watering from the haze until he couldn't do it anymore and he quit," Phuthon said. "He said he would die if he stayed."

Phuthon himself suffered from rashes and breathing problems, and he said his crops continue to suffer. He said APICO offered him compensation that does not begin to cover his losses.

Nirun said the human rights commission and the government had struck an agreement in early February to hold a forum for local stakeholders before drilling began, but the agreement was ignored. He said APICO officials "aren't announcing to the people about projects and exploration."

APICO is a privately held company incorporated in Delaware but based in Bangkok. It referred questions to its CEO, Dwight Johnson, who did not return repeated phone calls and emails from The Associated Press seeking comment.

The commission has been meeting with local communities for the past year and hosted a June meeting attended by 400 people. In total, petitions from eight communities in eight different provinces were filed against oil and gas exploration with the commission.

"We accumulated every single case and it boiled down to just one problem, which is granting concessions for natural resources should go through the legal process of environmental impact studies," said Kraisak Choonhavan, an adviser to the commission.

While APICO and Tatex have filed formal environmental impact assessments, Thailand's Environment Act requires that activities in the EIA be carried out only when locals are informed at least 15 days in advance. Chainarong said that according to residents, APICO obtained signatures granting consent to drill by giving away T-shirts, bags and nail cutters to villagers and making them sign for the items.

Phuthon, the rubber farmer, said that at the beginning of the drilling operation, APICO held an "educational session" telling residents the work would bring "jobs, ease of transport and civilization to the village." He said they offered souvenirs — "cheap things which cost less than 100 baht ($2.77)" — and asked people to sign their names as proof of receiving them. He said he took nothing.

The drilling dispute is taking place around the Dong Mun gas field, which covers 31.9 square kilometers (12.3 square miles) and has expected gas reserves of 96 billion cubic feet, enough to power about 1 million homes for one year.

In February, demonstrators from the town of Ban Na Dun in Khon Kaen blocked APICO's equipment from being transported to a drilling site, but soldiers, police and masked guards made them clear the road.

"I understand them, the villagers, when they said educated people took advantage of them," said Lt. Col. Napasit Pongwarapisarn, the provincial military chief of staff who attended the university conference. "I sympathized with them but what can the military do? Everything was signed. Military and police have to do it. We follow orders."

In late April, the group Stop Fracking Thailand staged a protest outside the U.S. Embassy demanding that American oil companies leave Thailand. In response, APICO representatives denied the use of fracking in northeastern Thailand.

However, Coastal Energy Company, a Cayman Islands-based company that owns a 39 percent stake in APICO, announced hydraulic fracturing tests at the northeastern APICO-operated gas fields in 2009 and 2010. Those tests were unsuccessful, and the company did not specify whether subsequent successful drilling involved fracking. Coastal Energy is now a subsidiary of Compania Espanola de Petroleos SA, which is owned by the Abu Dhabi government.

The EIAs for APICO and Tatex Thailand do not specify if the companies are using hydraulic fracturing but do detail onsite chemical wastewater ponds containing toxic materials such as arsenic, which are characteristic of fracking operations.

Phumee Srisuwon, director of Mineral Fuels Management Bureau for Thailand's Ministry of Energy, said fracking techniques have been used on a limited basis by state-owned energy company PTTEP, which has partnerships with APICO. He said those wells are in the northeast but would not say whether they are the same ones villagers are protesting.

He said fracking is "still in the early stage in Thailand."

APICO released a statement in early March saying that its obligations, including hosting meetings with locals in the affected areas, were met, and that the company's concession through the Thai government is legal.

Natural gas powers 75 percent of Thailand's electric power plants, and foreign companies account for more than half of the natural gas produced within the country. All the gas is sold back to the state, said Witoon Kaoaien, chief production supervisor for PTTEP.

Foreign companies are conducting both inland and offshore fracking operations in Thailand. Coastal Energy Company began using offshore hydraulic fracturing techniques in the southern province of Songkhla in 2013, according to its annual report.

Chevron uses seawater injection techniques at wells in the Gulf of Thailand's Pattani Basin. A 2011 research paper from the International Petroleum Technology Conference, authored by a Chevron Thailand Exploration and Production team, mentions Chevron Thailand's use of "prolonged hydro-fracturing" in this area, noting that the method fractures rock by injecting water, but differs from conventional hydraulic fracturing in that the cooling of the rock causes the fracturing, rather than high water pressure.

"Chevron does not apply hydraulic fracturing technology in Thailand," company spokeswoman Saransri Prawatpattanakul said in an emailed response to questions from the AP.

Many Thais have questioned the government's continued pursuit of fossil fuels, but it is risky to challenge military leaders who have maintained full control since a May 2014 coup.

Before the May conference, Chainarong said he was summoned to Maha Sarakham's city hall by Lt. Col. Napasit to sign an agreement forbidding criticism of Thailand's military government and allowing the officers to attend.

Napasit said in a telephone interview that the military and police had been invited to the conference. He described the document-signing as a normal procedure under the military government.

The lieutenant colonel was the last speaker at the forum. When he took the microphone, attendees rose from their seats and walked out.