Police are preparing to seek an arrest warrant for a woman in Bangkok accused of killing her teenage maid and concealing the body at her mother's home in Phetchaburi about five years ago.

Investigators were gathering information to support their planned application for an arrest warrant for Krisana Suwanphithak, 45, the maid's employer, after three persons of interest allegedly confessed to having assisted Ms Krisana in burying the body of Jariya Srisak, said Pol Col Phumin Phumphanmuang, chief of the Crime Suppression Division (CSD)'s Sub-division 5, yesterday.

The three who confessed to having been part of a plot to conceal the crime are an older brother of Ms Krisana, who is a village head in Phetchaburi, a daughter of Ms Krisana and another of the suspect's employees, Pol Col Phumin said.

The three, however, denied any involvement in the death of Jariya and insisted they had decided to help Ms Krisana conceal the corpse only because of their family connections to her, Pol Col Phumin said.

They told CSD investigators that Ms Krisana had a hot temper and said they had frequently seen her physically assaulting Jariya, he said.

During the Songkran festival of 2012, Ms Krisana had hit Jariya in the face with an aerosol can, which resulted in severe injuries, the witnesses said.

She then refused to take Jariya to receive medical assistance, said Pol Col Phumin, citing information provided by the three persons.

The trio said Jariya died the following day, which prompted Ms Krisana to ask for their help with taking the body to be buried near a sugar palm tree on the premises of her mother's home in Ban Na Mon Moo 7 in tambon Nong Sano of Phetchaburi's Muang district.

Police obtained a warrant to search the home of Ms Krisana's mother in Phetchaburi last month and found a human skeleton buried near the palm tree.

There remains were sent to the Institute of Forensic Science for further inspection and a DNA test.

"We are still waiting for the results of a DNA test to determine if the skeleton is indeed the remains of Jariya," Pol Col Phumin said.

A source said the results of the DNA test are expected to be known tomorrow.

Central Investigation Bureau (CIB) chief Thitiraj Nhongharnpitak said he had asked the investigators to expedite their efforts prior to warrants for the arrests of all suspects being issued.

On Friday, a source said Jariya's mother, Janthira Srisak, 48, travelled from Phetchaburi to Bangkok to seek help from the Pavena Foundation for Children and Women after she had been told by an unidentified witness last moth that her missing daughter had been beaten to death and her body buried five years ago.

According to the same source, the mother sought help from the foundation because she was well aware that the family of the suspected murderer is an influential one in Phetchaburi.

She had lodged a complaint with the local police in 2011 after having lost contact with her daughter while she was working as a housemaid at Ms Krisana's home in Bangkok.

The police later told her that Ms Krisana had insisted her daughter had run away, Ms Janthira said.

"I didn't believe it one bit that my daughter would ever run away without contacting me at all," she said.

"There had also been some unusual signs, which made me feel I was barred from keeping in touch with my daughter," the mother said.

The Pavena Foundation, a nonprofit organisation which provides assistance for women and child victims of trafficking and abuse, on Friday assisted Ms Janthira with lodging her complaint with Pol Lt Gen Thitiraj, after which the police secured their search warrant and eventually discovered the skeleton.

The source added that police on Friday night invited Pramote Suwanphithak, the village head of Moo 7 village in tambon Nong Sano in Phetchaburi's Muang district, to assist them in their enquiries into Ms Jariya's disappearance and the discovery of the body.