The Appeal Court has upheld sentences of 10-years in prison for two of five defendants in the "men in black" case arising from the violent clashes between protesters and security forces during the political upheaval of 2010.
Three other defendants were again acquitted.
The court’s ruling was read out at the Criminal Court on Wednesday.
The defendants in the case brought by prosecutors were - Kittisak Soomsri, 49, of Bangkok; Preecha Yuyen, 29, of Chiang Mai; Ronnarit Suricha, 38, of Ubon Ratchathani; Chamnan Phakheechai, 50, of Bangkok and Ms Punika Chusri, 44, of Bangkok.
They were accused of illegal possession of firearms, ammunition and explosives and carrying them in communities or public places without permission.
The prosecution case presented to the court was that the five defendants and accomplices who were still at large and some who later died had carried firearms, ammunition and explosives - such as an M79 grenade launcher, an M16 rifle and an HK33 rifle - to Khok Wua intersection, Tanao Road and Prachathipatai Road in Phra Nakhon district during the red-shirt protest against the Abhisit Vejjajiva administration on April 10, 2010.
The United Front for Democracy against Dictatorship (UDD) was staging demonstrations covering areas from Pin Klao Bridge throughKhok Wua intersection to Phan Fa Bridge on Ratchadamnoen Avenue on April 10, 2010. Soldiers were ordered in to clear protest sites at 2pm that day.
The so-called "men in black" appeared and opened fire on the soldiers as well as protesters. The clash at Khok Wua intersection resulted in the deaths of 26 people, including five soldiers and one Reuters journalist.
On Sept 11, 2014, officers arrested the five defendants and handed them over to the Department of Special Investigation.
On Jan 31, 2017, the Criminal Court found Mr Kittisak and Mr Preecha, the first and second defendants in the case, guilty of illegal possession of firearms, ammunition and explosives and sentenced them to eight years in jail each. The court also sentenced the two defendants to two years in jail for carrying those firearms in public areas without permission.
The lower court acquitted the third to fifth defendants, but ordered them detained pending the state's appeal.
Prison officials on Wednesday took Kittisak and Preecha from Bangkok Remand Prison to hear the Appeal Court’s ruling. The three other defendants, who had earlier been allowed bail by the court, were also present for the reading of the judgement.
The Appeal Court upheld the lower court’s conviction and sentencing of Kittisak and Preecha to 10 years in jail.
The court upheld the acquittal of the three others, but ordered their detention pending the state's appeal to the Supreme Court and its decision on bail.