The order came after controversial images of police officers and suspects in the gruesome killing of karaoke singer Warisara Klinjui seemingly in a relaxed mood were leaked onto social media.

Police adviser Kavee Supanun said police officers must be aware that they had to be neutral and should not tarnish the force’s image.

Meanwhile, an investigation was ordered into the photos and video clips featuring the three suspects, who surrendered at the weekend.

In announcing the probe, police spokesman Pol General Detnarong Suthicharnpanya referred to the case of Priyanuch Nonwangchai, Kawita Rachada and Apiwan Satayabundit, who were arrested on warrants for allegedly murdering Warisara in Khon Kaen and cutting up her body last month.

They escaped to Myanmar through Chiang Rai’s Mae Sai district on May 25 after allegedly killing Warisara, reportedly out of a personal grudge over a drug case, and dismembering her body. All three surrendered to Myanmar police on Saturday night and were then handed over to immigration police in Chiang Rai on Sunday.

One of the controversial photos showed Priyanuch with white powder on her face smiling and taking a picture with police, who also smiled for the camera. Another photo showed Kawita and Apiwan busily doing their makeup.

Television footage aired nationwide on Sunday showed one of the suspects about to open a bottle of water before a police officer took it and opened it for her. The photos and clips were leaked on social media, drawing criticism that police seemed eager to please suspects who had been charged with such a grisly murder.

Netizens also cricised the suspects for failing to show real remorse for the murder.

The three were also apparently not handcuffed when handed over by Myanmar authorities to Thai police, which was claimed to be against the rules. However, police handcuffed the suspects when they took them for a re-enactment in Khon Kaen yesterday.

Detnarong said the Immigration Police Bureau had been ordered to set up a fact-finding committee to look into the case.

“At this stage, I believe the actions may be a police strategy to make the suspects relax so that they will reveal some information,” he said.

He implied that the suspects had told police the name of another male suspect who had participated in the murder as a result of the relaxed treatment.

Five suspects are now in police custody, including Wasin Namprom and Jidarat Promkhun. Wasin named Priyanuch as the killer, insisting he was only a driver, while Jidarat claimed she had been tasked with selling Warisara’s belongings.

However, Priyanuch told police on Sunday that Wasin had been involved in the murder. The five have been charged with murder, hiding a body and robbery.

The spokesman asked for the public to be confident that the police would not discriminate against or favour any suspect.

Meanwhile, a woman who identified herself on Facebook as a lawyer with the name of Zara Wf Gwang wrote that the suspects’ rights were protected by law, including the provision of food, medicine and medical care regardless of the charges they were facing.

She said the treatment given to the three suspects was not as good as many had claimed from what she had seen.

Regarding the handcuffs, she wrote that the circumstances of a suspect’s detention should depend on the situation, adding that suspects would be handcuffed when brought to court and to prison. However, she said she did not feel any sympathy for the suspects.