Police asked Ratchadapisek Criminal Court to detain the man for 12 days while they await the results of forensic tests. Officers feared the suspect might flee and said they needed to question him further.

The court agreed not to grant bail to Sirimongkol Reunnak, 33, on grounds that the crime had shocked the public.

The judge ordered Sirimongkol to be detained at Don Muang police station for 12 days.

The schoolgirl suffered multiple knife wounds and appeared to have been sexually assaulted. Police were checking the girl's possession as the suspect had claimed his motive was to rob her.

Sirimongkol, who was arrested on Friday in Buri Ram, has allegedly admitted he robbed and killed the girl. He has denied raping her.

Police said they will charge Sirimongkol immediately if his DNA matches samples found on the girl. Conviction for rape and murder could draw a death sentence.

At 6am yesterday, police took Sirimongkol to re-enact the crime. This was done without advance notice to avoid further incidents after 600 angry onlookers tried to attack the man on Saturday during an earlier re-enactment attempt.

Don Muang superintendent Colonel Chatuphan Wannapak said the re-enactment was done at four sites. The first location was where the suspect - disguised as a motorcycle taxi driver - picked the girl up on Thursday night. The second spot was where he allegedly raped and killed the girl. The third spot was where he threw the knife into a canal, and the fourth was Sirimongkol's home in Pathum Thani's Lat Lum Kaeo district, where he allegedly disposed of his blood-stained shirt.

Chatuphan said the suspect had said he would confess to the rape charge if doctors could find his semen or pubic hair on the girl.

Police suspect Sirimongkol punched the girl in the stomach but she managed to run away. He allegedly chased her and stabbed her three times before raping her.

The initial forensic report said the girl did not die immediately from the knife attack, Chatuphan said, so police conducted a complete crime re-enactment including the alleged sexual assault.

"It should not be a problem. We now only have to wait for the results from the Forensics Office. But police have not charged the suspect with rape yet pending clearer forensic evidence," he said.