An army general in Thailand was one of the most prominent figures found guilty in a major human trafficking trial that included more than 103 defendants accused of involvement in a modern-day slavery trade.

Lieutenant-General Manas Kongpaen was convicted on Wednesday of several offences involving trafficking and taking bribes.

At least one other defendant considered a kingpin in the illegal trade, Pajjuban Aungkachotephan, was also found guilty. He was a prominent businessman and former politician in the southern province of Satun.

By Wednesday evening, 62 people were found guilty, with sentences ranging from four years to the maximum 50 years allowed under the criminal code, officials said. Individual sentences were not immediately announced.

READ MORE: Thailand and the daily travail of human trafficking

As well as the general, Myanmar nationals, Thai police officers and local politicians are among those accused.

Arrests began in 2015 following the discovery of 36 bodies in shallow graves in southern Thailand.

That discovery exposed networks which trafficked Rohingya Muslims fleeing persecution in Myanmar and held them for ransom in jungle camps before they were granted passage to Malaysia.

The trial began that year, when authorities said traffickers held migrants in the camps as hostages until relatives were able to pay for their release.

Many never made it out.

The case drew special attention when its lead police investigator, Major-General Paween Pongsirin, fled to Australia and said he feared for his life after his findings implicated "influential people" in Thailand who wanted to silence him.

Thailand's military government has said it is making the fight against human trafficking a national priority.

Thailand has yet to release a full report on the graves and the results of post-mortem forensic testing.

Rights groups say trafficking networks were largely left intact by the 2015 crackdown and trial.

"We believe that the crackdown is only a disruption of a trafficking network but that network is still very much well in place," said Amy Smith, an executive director of rights group Fortify Rights.

Smith also said the current trial has a narrow focus.

"We expect there are many more perpetrators out there," she said. "This is a big business with big money."

Sunai Phasuk, a senior researcher on Thailand at Human Rights Watch, said: "There needs to be more prosecution against traffickers as well as more work on rehabilitation of trafficking victims."

Lengthy legal process

The legal process in handing down verdicts is lengthy in Thailand, and it may take hours before the judge reveals the exact details of the verdicts to a packed Bangkok court.

The trial has been marred by allegations of intimidation against witnesses, interpreters and police investigators.

Thitinan Pongsudhirak, director of the Institute of Security and International Studies at Chulalongkorn University, said this trial will serve as a litmus for Thailand’s military government, which is marred by controversies and corruption scandals.

"Overall, this case is going to decide whether this government has any lasting legacies or achievements at all and they are putting a lot of emphasis on the trial to show its credibility," he told Al Jazeera, from Bangkok.

Thailand's government denies that trafficking syndicates are still flourishing and has said it has largely eliminated human trafficking in the country.

Journalists were not allowed in the court room on Wednesday, but proceedings were relayed on television screens provided by the court.

Thailand has historically been a source, destination and transit country for men, women and children who are often smuggled and trafficked from poorer, neighbouring countries including Cambodia, Laos and Myanmar to work in Thailand or further afield in Malaysia, often as labourers and sex workers.

Mass grave

Last month the US state department left Thailand on a Tier 2 Watchlist, just above the lowest ranking of Tier 3, in its annual Trafficking in Persons (TIP) Report because it did not do enough to tackle human smuggling and trafficking.

Al Jazeera's Scott Heidler, reporting from Bangkok, said the scale of the trial meant the verdicts would take several hours to read and the hearing could last into tomorrow.

"Most [human rights] observers are hoping that there are going to be follow-up cases because they also believe - when you look at this case - we're looking at a very small area; this one mass grave they found along the border in 2015 and one ring that supplied those camps with the people coming across down from Myanmar," he said.

"Human rights observers are hoping that this is just the beginning and there will be many more cases to come."

All the defendants earlier pleaded not guilty and were placed under pre-trial detention.