The chief constitution writer has taken over scrutiny of police reform. (File photo)

A committee scrutinising a bill on police reform has agreed to draft another police-related law with the aim of improving the effectiveness and efficiency of police criminal investigations.

The panel chaired by Constitution Drafting Committee (CDC) chief Meechai Ruchapan would be responsible for drafting the proposed law which would give prosecutors a role in handling criminal investigations.

Committee member Kamnoon Sidhisamarn said the proposed "investigation" bill, which is hoped to supplement the Criminal Procedural Code, will assist and support the integrity of police criminal investigations.

The panel was set up to draft and vet the reform-related law and is part of the Council of State, the government's top legal advisory body.

While a wide range of issues has yet to be discussed and finalised in the proposed bill, Mr Kamnoon said it was agreed initially that police officers tasked with the suppression and prevention of crime will be authorised to assist investigators as allowed by the law or as requested.

It is also hoped the proposed bill will provide convenience for the public who will be able to lodge complaints at any police station, instead of the station with jurisdiction over where an offence has taken place, he said.

Police officers who accept the complaints are required to conduct a preliminary investigation and hand over the initial findings to investigators at the station with jurisdiction, according to Mr Kamnoon.

Among other issues being thrashed out include the appointment of specialists from other agencies as police assistants or consultants.

Deputy Prime Minister Wissanu Krea-ngam said it is possible that prosecutors may join police in the investigation process.

He noted the idea of letting prosecutors have a role in investigating criminal cases has been around for some time and the issue had been on the agenda of the now defunct National Reform Council and National Reform Steering Assembly.

He said that prosecutors could join police probes in serious and high-profile cases such as national security and human trafficking.

Currently, prosecutors decide whether to indict a suspect based on a police investigation summary.

Some legal experts think it would be useful if prosecutors actively join a police investigation, which could make a case watertight.

On Tuesday, Council of State secretary-general Distat Hotrakitya confirmed that Mr Meechai's panel would draft the new bill.

The panel scrutinising the police reform bill was established after the CDC argued the reform blueprint proposed by a committee led by former supreme commander, Boonsrang Niumpradit, fell short of the radical restructuring needed for the Royal Thai Police.

The committee is expected to observe six reform frameworks laid down by the prime minister, which are the new structure of the police force; its scope of power and responsibilities; promotions and transfers; budget allocation; the use of forensic science; and welfare benefits for police officers.