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

Police adviser Kavee Supanun said every police officer must aware that they have to be neutral and should not do any deeds that could 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 dismembered 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 on the controversial photos showed Priyanuch with white powder on her face smiling and taking a picture with police, who also smiled to 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.

The three were also apparently not handcuffed when handed over from 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 on Monday.

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 would reveal some information,” he said.

He implied that as the results of the police approach, the suspects told them the name of another male suspect who had joined in the murder.

Five suspects are now under police custody, including Wasin Namprom and Jidarat Promkhun. Wasin named Priyanuch as the killer and the one who mutilated the victim, 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 was involved in the murder. The five have been charged with murder, hiding a body and robbery.

The spokesman called for the public to have confidence that the police would neither discriminate against nor favour any suspect.

Meanwhile a lawyer who identified herself on Facebook as Zara Wf Gwang wrote that any suspect’s rights are protected by law, including the provision of food, medicine and medical care. The suspects were entitled to this no what they were charged with, she wrote.

She said that from what she saw, the treatment given to the three suspects were not quite so good as many had claimed.

Regarding the handcuffs, she wrote that detention of a suspect should be implemented at the necessary level, saying the suspects would be handcuffed when brought to court and prison. She added, however, that she did not feel pity for the suspects.