Prosecutors told a court in the south-western city of Kunming, capital of Yunnan province, that Nor Kham and his five accomplices were accused of murder, drug trafficking, kidnapping and hijacking ships.
His five co-accused all admitted the charges against them and said the attack on two Chinese ships was planned a led by Nor Kham, the official Xinhua news agency said.
But Nor Kham denied any involvement in the case when questioned in court on Thursday, despite reportedly confessing his involvement to police.
The semi-official China News Service said prosecutors asked him if he commanded and took part in hijacking Chinese ships, killing the ships' crew and planting drugs on the vessels.
Nor Kham denied all charges and said: "The (crime) was carried out by the Thais. I knew about it through television." Earlier reports quoted Chinese police as saying they believed Nor Kham's gang had colluded with Thai soldiers.
The agency quoted Liu Yuejin, director of the Ministry of Public Security's anti-narcotics bureau, as saying Nor Kham's denial of all charges was unlikely to change the course of the trial.
"Even though Nor Kham withdraws the confession, it won't change the facts of the crime because the evidence is conclusive," Liu was quoted as saying.
Myanmar citizen Nor Kham, 44, was extradited from Laos to China in May following joint operations by police from Thailand, Laos and China.
State broadcaster China Central Television identified two co-defendants from Myanmar by the Chinese names Zha Bo and Zha Tuobo.
Two more defendants with Thai and Lao nationality were named as Sangkang Zhasa and Zha Xika, while the sixth defendant, Yi Lai, was reportedly stateless.
The official Xinhua news agency quoted Dong Lin, the court's vicepresident, as saying before the trial that it was "uncommon in China's judicial practice for foreigners who commit crimes against Chinese nationals outside China to be brought to justice before aChinese court."
Reports said relatives of the 13 Chinese victims and embassy personnel from the defendants' countries attended the trial, which would continue until Saturday.
Xian Yanming, Yunnan's deputy police chief, told the China Dailynewspaper earlier this week that Nor Kham's gang had "colluded with renegade Thai soldiers in premeditated attacks on Chinese ships."
They wanted to "make it appear that the (Thai) authorities had uncovered a major drug-related case" by planting drugs on the shipsand pretending that the Chinese sailors were drug traffickers who died in a shoot-out, Xian said.