Justice Minister Paiboon Koomchaya has instructed new Department of Special Investigation (DSI) chief Suwana Suwanjuta to leave it to the agency's Special Case Committee to choose which cases to investigate.
The minister announced the policy to Ms Suwana and DSI executives Wednesday, a day after the new chief started work.
Ms Suwana was appointed director-general by the cabinet on Tuesday and is the first female official to lead the DSI.
"The DSI director-general and agency's other units will be given three days to come up with details on how the Special Case Committee will choose cases to investigate," Gen Paiboon said.
"This will prevent the power to choose cases for investigation from falling into the hands of just one person," he said.
He noted that flaws had been found with DSI work lately after the agency allowed politicians to interfere with its operations.
Under the original spirit of the DSI, the Special Case Committee was asked to decide which cases would be picked up for investigation.
However, over the past three or four years, it appeared DSI chiefs had been able to exert excessive power over the committee and influence the selection of cases the agency would probe, the minister said.
Although the law stipulates there are 36 types of case which the DSI can take up for investigation automatically, there are certain types of cases the agency is required to consider thoroughly before investigating them.
Gen Paiboon said his policy of returning decision-making power to the Special Case Committee may cause some delays in the DSI's work, but it should enable the agency to execute proper judgement when choosing cases.
The minister said he had also asked the DSI to send details on cases that are more than 80% complete to him so they can be reviewed.
Gen Paiboon said he wanted to find out which types of case the DSI has been choosing to investigate, and why the agency has been criticised over their selections.
He also wanted to find out whether the DSI had chosen some cases on the orders of senior figures.
According to the minister, the aim of the case review was not to find fault with officials, but to find out if the investigations had affected innocent people.
"As for political cases, I have made it a policy that the DSI will not be biased towards any investigations into colour-coded groups," he said.
"Investigators should not provide preferential treatment to the subjects of their probes because they are members of the People's Democratic Reform Committee or the United Front for Democracy against Dictatorship," Gen Paiboon said.
"They all must be treated equally as Thais," the minister added.
The DSI will also be asked to provide information on the status of cases relating to attempts to overthrow the monarchy such as lese majeste probes.
Information on forest encroachment cases would also be sought by the DSI.
Ms Suwana said it was a clear policy of Gen Paiboon's that the DSI must work in compliance with the law and ensure that personal beliefs did not intrude on investigations.
The new DSI chief also urged her subordinates to work with dedication to restore the image of the agency.
"The DSI's image is in trouble and the only way to correct it is by cooperation from the department's knowledgeable personnel," Ms Suwana said.
She said she expected all members of the agency to join forces and pull their weight in restoring the DSI's image.
Ms Suwana said she would meet the DSI's deputies director-general and directors of each crime bureau today to draw up criteria to be used by the Special Case Committee when choosing cases.