Last week's murder and dismemberment of a South Korean man should teach the police a lesson -- that criminals can use Thailand's porous natural border to get in and out of the country undetected with ease.
The case grabbed public attention on Jan 21, when the headless body of a man was found in a forest reserve in the seaside province of Rayong. His torso was found separately, along with the first clue to the man's identity -- a tattoo of a geisha on the back.
The body was identified as 38-year-old South Korean national Choi Myonghoon.
Choi had been arrested by Thong Lor police in Bangkok on June 25, 2015, and charged with illegal gambling before he was deported and blacklisted from Thailand, said Pol Col Arun Wachirasrisukanya, chief of the Crime Suppression Sub-Division 2.
Three days after the body parts were found, 32-year old Gim Hyeonjun came to the South Korean embassy in Bangkok, claiming to have knowledge about Choi's murder. It was the embassy who handed him over to the Crime Suppression Division (CSD).
During questioning, Mr Gim's testimony proved to be the key to unlocking the gruesome murder mystery.
Mr Gim said he worked as a programmer and he had invested in an online gambling site with two other South Korean citizens -- Kim Changhoon, 32, and Choi, with whom he had been arrested in 2015.
He said Choi had cheated on them in the business, and that in a fit of rage, Mr Kim killed Choi using equipment brought over by Yang Chonyo, 26, who was identified in earlier reports as "Mr K".
Mr Gim also said he was forced to watch the murder, or he would be killed too.
"Later, Mr Gim felt he should report the murder to the police, hoping he would be treated as a witness," Pol Col Arun said.
Subsequent investigations by the CSD found that Choi, Mr Gim and Mr Kim had broken away from a major gambling operation based in Cambodia to set up an online betting service in Thailand.
Choi, Mr Gim and Mr Kim have been put on the Thai immigration blacklist since their June 2015 arrests. Yet somehow, the trio managed to return to the country undetected earlier this year and set up their own gambling operation.
In the business, Choi was the financier while Mr Kim took care of accounting. The three lived together in a rented apartment, which doubled as the headquarters of their gambling operation.
On Jan 16, Mr Kim had a heated argument with Choi over a business conflict. Mr Gim said he heard the quarrels and went out of his room to check out what was happening, only to be told by Mr Kim he had murdered Choi in the bathroom.
Pol Col Arun: 'Mr Gim felt he should report the murder to the police'
Mr Gim said he was forced to stay in the apartment with Mr Kim, and told to witness the dismemberment, said Pol Col Arun.
Pol Col Arun said Mr Kim then called Mr Yang to bring in the equipment to cut up the body.
Choi's head was packed inside a shoulder bag and thrown into the sea.
After that, the men left the apartment and went their separate ways, said Mr Gim, who insists that he had no part in Choi's murder.
Police nabbed Mr Yang at a condominium near the Central Plaza shopping centre in Rayong, less than 24 hours after Mr Gim was handed over to the CSD.
On the same day, the police tracked Mr Kim's mobile phone transmissions and arrested him about 80km from the Thai-Cambodian border in Ban Pakkard, Chanthaburi province.
The three men have been charged with Choi's murder and conspiring to conceal and destroy his body.
Currently, the police are trying to figure out the point-of-entry along the Thai-Cambodian border that the men used, said Immigration Bureau chief Pol Lt Gen Surachate Hakparn.
Pol Lt Gen Surachate Hakparn said that despite a rise in the number of crimes committed by South Korean nationals in Thailand, overall they account for a small percentage of criminals in the country.
Their number is comparatively smaller than the number of fugitives from other countries, such as India and China, said Pol Lt Gen Surachate.
In the aftermath of Choi's murder and mutilation, the immigration police are stepping up its cooperation with other related agencies to improve border patrols so that criminals won't be tempted to exploit Thailand's natural borders to enter and leave the country illegally, he said.