UTHAI SAWAN: Thousands of people gathered at temples in northeast Thailand on Tuesday to cremate the victims of a massacre of 36 people, among them 22 preschool children slashed to death in a rampage by a disgraced policeman that shocked the world.

Crowds gathered around the normally sleepy town of Uthai Sawan to lay flowers and join queues of mourners, who paid their last respects to those slain in a three-hour gun and knife attack on Thursday that marked the worst massacre in Thailand's recent history.

Orange flames lit up the smoke-filled sky outside the Rat Samakee temple in Uthai Sawan late on Tuesday, as a line of funeral pyres for 19 of the nursery school victims was set ablaze in front of family seated behind a small gravel path.

Earlier, white coffins were carried by relatives and police officers, one by one to the site of the cremation along a route lined with mourners, led by family members carrying portraits of the dead - a teacher and 18 children aged between 2 and 5.

"The teacher will take the lead and the 18 children will follow her steps to heaven, according to our beliefs and the desires of their parents and everyone here to send them off," said the temple's abbot, Prakru Adisai Kijjanuwat, as the ceremony began.

The coffins were placed on pyres newly built from bricks and dressed with flowers and black and white decorative cloth.

Atop the caskets were pictures of those killed, some accompanied by stuffed toys, as orange-robed monks performed rites.

Police identified the attacker as Panya Khamrap, 34, a former Bangkok police sergeant who was discharged in January after being in possession of methamphetamines. He was on trial on drugs charges and was in court the morning of his attack.

His killing spree ended at his home about 3 km (2 miles) from the nursery, when he turned his 9 mm handgun on himself, after killing his partner and her child.

An autopsy of Panya's body showed no signs of drugs use on the day of the murders, police said.

They said their investigation indicates his rampage was the result of excessive stress from the loss of his job and a breakdown in his relationship.

Prime Minister Prayuth Chan-ocha, who attended the ceremony in Uthai Sawan ahead of the cremations, on Monday ordered law enforcement agencies to tighten gun ownership rules and crack down on drug use following the mass killing in Uthai Sawan, 500 km (310 miles) northeast of Bangkok.