The man, known only as Nui, committed the crimes in Bangkok last December.
His own life was spared by the court on grounds that he confessed.
Suspect serial rapist, killer
Nui, 36, was arrested after security video showed that the young girl was last seen with him late on December 6.
After his arrest, evidence emerged that Nui might have been a serial rapist and killer.
“There is solid evidence against him relating to the disappearances of at least two other children in Loei,” Elaluk Lhumchomkhae
of the Mirror Foundation said.