Police are not convinced serial killer Somkid Pumpuang did not plan to murder a 51-year-old Khon Kaen woman, after he confessed to the crime on Thursday.
Pol Col Boonlue Phadungthin, head of Crime Suppression Subdivision 3, said on Thursday Somkid claimed he killed Ratsami Mulichan in a fit of rage at her home in tambon Nong Tako in Kranuan district on Sunday.
However, investigators do not believe his story. Evidence suggested he planned the murder.
Three days before the killing, Somkid told Ratsami he was taking her motorcycle to be repaired in downtown Khon Kaen. Police said no repairs were made as the motorcycle was left at Khon Kaen Hospital.
Investigators suspected it was used as a getaway vehicle after the murder. He drove the motorcycle to Buri Ram where he boarded a train bound for Bangkok.
Somkid was familiar with Buri Ram because one of his previous victims lived there.
The killer, dubbed the "Jack the Ripper of Thailand" by the media in 2005, was arrested on the Bangkok-bound train at Pak Chong station in Nakhon Ratchasima late on Wednesday morning.
He is accused of strangling Ratsami, who worked as a hotel maid. The victim's son said Somkid claimed to be a lawyer when he got to know Ratsami via Facebook. He moved in with her on Dec 2.
Pol Col Boonlue said on Thursday that during his escape after Sunday's killing, Somkid dropped a mobile phone in Khon Kaen to throw police off the scent.
The police found the phone belonged to Somkid's girlfriend Sumalee (surname withheld), who has been seeing him since his release from jail.
According to Pol Col Boonlue, Somkid met Ms Sumalee in June and they moved in together in Rayong where they ran a noodle shop. Ms Sumalee did not know Somkid was a convicted killer. He told her he practised law.
While living with her, Somkid met Ratsami and started a relationship with her.
Somkid told Ms Sumalee he would be away working in Khon Kaen when in fact he was spending time with Ratsami.
He coaxed her into paying a down payment on a car.
Realising he could not afford the installments, he tried to break up with Ratsami and they had a fight, during which he killed her, Somkid claimed.
Despite confessing to the murder during an interrogation that lasted all night following his arrest on Wednesday, Somkid refused to re-enact the crime, saying it would be too stressful, police said on Thursday.
However, he agreed to a re-enactment of his escape, Pol Lt Gen Charoenwit Sriwanit, head of Provincial Police Region 4 said.