Its completed report on the 2010 political unrest unveiled on Monday also blamed the security forces for poor handling of the protesters and criticised the military coup in 2006 which stirred political problems in the country.
Somchai Homla-or, who heads the TRC's fact-finding sub-committee, said the commission probing the bloody events between March and May 2010 found connections between the "men in black" and security guards of the United Front for Democracy against Dictatorship in at least two clashes with authorities at Kok Wua intersection near the Democracy Monument and the Pratunam area on April 10, 2010.
Many of the "men in black" were found to be close to Maj Gen Khattiya, but "we do not have evidence to conclude whether they had a connection with UDD key figures", said Mr Somchai.
Maj Gen Khatthiya, an army specialist, was shot dead by a sniper while talking to reporters near a subway exit at Lumpini Park during the red shirts' anti-government protest on May 13, 2010.
The clash at Kok Wua killed four soldiers including Col Romklao Thuwatham while an attempt was being made to contain a mob of red-shirt protesters.
According to evidence compiled by the commission, the "men in black" fired M67 hand grenades, M79 rocket-launched grenades and rifles at soldiers at Kok Wua on the night of April 10, 2010. Col Romklao, who was posthumously promoted to general, was killed by one of the M67 hand grenades, it added.
The TRC says in its report that 92 people died as a result of the protests, but did not add a death at Saman Metta Mansion in Nonthaburi's Bang Bua Thong district and other places to the list.
The commission stopped short of declaring that the deaths of protesters and a nurse at Wat Prathum Wanaram on May 19, 2010 were due to shots fired at them by soldiers. The deaths were "possibly" due to the soldiers shooting into the temple, it said. A group of armed protesters also fired from the temple or in front of the temple at the soldiers stationed on the BTS track, it added.
The TRC also criticised the handling of the protesters by security forces as they used war weapons and "improper" tactics including firing tear gas from helicopters which stirred panic and mistrust among the demonstrators.
It said the failure of the checks and balances system under then prime minister Abhisit Vejjajiva had led to street rallies against the government.
It added the military coup on Sept 19, 2006 did not solve political problems and instead jeopardised the rule of law in the country.