Nui have raped nine children, four of whom he murdered, including six-year-old Nong Cartoon.
The man, 34, is identified variously as Nui or Tin Tang or Khun Dej and does not have a family name. He was never issued an official identification card.
Prosecuters earlier told the Criminal Court that on Nov 10, 2013 Nui asked a seven-year-old boy to go with him on a bicycle from Wat Si Udom in tambon Si Songkhram of Loei's Wang Saphung district, where a tod krathin ceremony was being held. When the boy refused, Nui forcefully took him to the top of Phu Pha Sing mountain near Ban Non Somboon in tambon Nong Ya Plong of the same district.
Nui raped the boy, gripping his throat with his hands until he became unconscious and died.
Nui then wrapped the naked body in a blanket and put him in a fertiliser sack, along with the boy's shorts, shirt and sandals. The sack containing the body was left at the scene of the murder.
The man was later arrested for sodomy, murder, concealng a dead body and other related charges.
The Criminal Court on Nov 17, 2015 sentenced Nui to death. The sentence was commuted to life because he confessed. The case was forwarded to the the Appeals Court.
The Appeals Court upheld the lower court's life sentence on Nui. The court stated that although there were no eyewitnesses, the defendant's confession to the charges was sufficient.
After the ruling was read out, Nui's lawyer said he would take the case to the Supreme Court because the two lower courts' judgements were based on circumstantial evidence, without actual witnesses. The Supreme Court's judgement would set a precedent for similar cases in the future, he said.
Nui had earlier been sentenced to life sentences in two other cases.
In July 2015, Nui received life imprisonment, commuted from death, for the attempted rape and then murder of a 4-year-old girl in Muang Loei district of Loei on Feb 5, 2013.
In March 2014, he was sentenced to life for the rape and murder of a 6-year-old girl known as Nong Cartoon.
He lured her from her parents’ pickup truck, where she had been left alone, and attacked her on a vacant area of land close to Bearing BTS station in Bang Na district, Bangkok, on Dec 6, 2013.
Nui was arrested on Dec 15, 2013 for the rape and murder of Nong Cartoon.
According to police, Nui grew up in an orphanage and a couple adopted him when he was 7 years old. He lived with them in Puai Noi district, Khon Kaen province. When he was 15, his adoptive parents died. He went to live with their relatives in the same district.
Nui never had schooling. Without an ID card, he worked as a labourer at construction sites and fairs in various provinces.
His first victim was a 7-year-old girl who went to a temple fair alone in Puai Noi on Jan 18, 2008.
He tried unsuccessfully to rape her, then to strangle her.
The girl, however, survived, and identified him following his arrest.
He served three years and eight months in prison in Phon district of Khon Kaen and was released on Aug 23, 2012.
After his release, Nui returned to his former village in Puai Noi district, but the locals rejected him for fear he would prey on other children.
He told police he had attacked about 10 children, and killed four of them.
Outrage in Thailand as girl, 13, is raped and strangled JILL REILLY 9 July 2014