The victims were sexually assaulted while they were just between seven and eight years old.
The crimes took place at a Bangkok-based school as well as at a hotel in 2006.
The two defendants were Lon Sorakanit, 68, and Pimol Sunsri, 58. Both threatened their victims not to tell anyone about the sexual attacks but the girls’ parents discovered what happened and lodged complaints.
The Supreme Court convicted both defendants, ordering Lon to serve 19 years and three months in jail and Pimol to serve 12 years in jail.
Both convicts showed no expression when they heard the verdict.
They have been behind bars since the lowest court found them guilty in 2007. Back then, they were sentenced to 50 years each.