The woman, in her 40s with dyed blonde hair, was spotted early in the morning on Aug 18. Her hands and feet were tied and burn marks were visible on her back.
Ayutthaya police chief Kornake Petchaiwes supervised the investigation, with the province's experienced investigator Pol Col Suthep Chanasit spearheading the probe.
Pol Col Suthep found that the victim had died from asphyxia. Traces of latex glue were found on the victim's body. Police thought it may have been used to set her on fire.
Officers were deployed to check CCTV footage and comb areas around the crime scene. Provincial Police Region 1 investigators searched camera footage on roads in and out of the province and checked missing-people records.
As news about the murder spread, police were contacted by the woman's relatives, who identified the victim as Kankanit Suntratta, 42, from Bangkok.
Pol Col Suthep then started poring over Kankanit's belongings for clues. Her mobile phone was still missing, but Kankanit's younger sister later told police the victim had a computer notebook.
Pol Col Suthep managed to obtain the laptop and started checking hundreds of photos on it.
He spotted a photo of a contract showing Kankanit had offered a loan of 300,000 baht to Jakkraphun Kanjadara in 2010.
Police then went to Mr Jakkraphun's house in Pathum Thani's Lat Lum Kaeo district, but learned he had leased the house to others. They also found no sign of him at his parents' house.
Pol Col Suthep took a closer look at the contract and found that someone by the name of Supapan Chainat had witnessed the agreement. The officer thought Ms Supapan was possibly Mr Jakkraphun's wife.
Pol Col Suthep ordered officers to stake out Ms Supapan's house on Phraya Suren Road in Bung Kum district.
Last Monday night, Mr Jakkraphun arrived at the house and was arrested.
Police scoured several documents taken from the suspect and found a piece of paper indicating he had taken his car for repairs just hours earlier.
Officers took Mr Jakkraphun's clothing for examination and found bloodstains on a pair of his trousers.
Mr Jakkraphun initially denied the murder allegation, saying he had only met Kankanit to settle the debt and left her before the body was found.
The interrogation ran overnight.
A forensic test found the bloodstains on the suspect's trousers matched the blood of the victim, arming police with a crucial piece of evidence.
"The interrogation dragged on until 6am, so I decided to show him the blood evidence, and he was speechless," Pol Col Suthep said.
Mr Jakkraphun eventually admitted to being responsible for the death, but insisted he did not intend to kill the victim, Pol Col Suthep said.
The suspect allegedly said he picked up Kankanit on Ram Intra Road and then a heated argument broke out.
Mr Jakkraphun said Kankanit tried to kick him, causing the vehicle to strike a roadside barrier.
He tied her up after she lost her temper with him, Pol Col Suthep said.
She kept threatening and scolding him so he covered her mouth with duct tape and covered her head with a plastic bag, he said.
The victim died some time later and Mr Jakkraphun dumped her on the side of the road before setting her body on fire in an attempt to destroy the evidence, according to the alleged confession.
Pol Col Suthep said the suspect told them he had taken the victim's car to a deserted construction site in Phatthanakan Soi 26.
The vehicle once belonged to Mr Jakkraphun as he placed the car as a guarantee for the debt payment to Kankanit.
Pol Col Suthep said the police plan to add car theft charges to the case against Mr Jakkraphun.
If it could be proven that the murder was premeditated, the suspect would face harsher charges, he added.
"The case was solved quickly because of teamwork," Pol Col Suthep said. "Everyone helped share information and nobody withheld information to try to become a lone hero."
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