Human rights advocates have slammed the regime's decision to give soldiers powers, on par with police, to deal with crime, which they say could lead to unrestrained actions and abuse of power.
The regime claimed a shortage of police officers as a key factor behind its decision.
Prime Minister Prayut Chan-o-cha's order shows an ongoing trend by the National Council for Peace and Order (NCPO) to enforce unchecked powers with total impunity, said Human Rights Watch researcher Sunai Phasuk.
There are no check or oversight mechanisms regulating actions carried out under the government's plan to crack down on "mafia" and "influential criminal figures". That is very alarming, Mr Sunai argued, especially since the NCPO does not tolerate any form of scrutiny or criticism.
- Earlier report: Soldiers get police powers of arrest, seizure
Human rights violations could ensue, he said, while the order reflects the junta's disregard for procedures.
"It reaffirms that Thailand has become a military state" as many tasks are being transferred into the hands of soldiers, he said.
Soldiers from the rank of sub-lieutenant up have been given police powers to summon, arrest and detain suspects by an order under Section 44 of the interim charter issued on Tuesday.
They are also authorised to conduct searches, seize assets, suspend financial transactions and ban suspects from travelling.
Soldiers can search any property they believe is linked to suspects or their assets. The searches can be conducted on individuals and vehicles.
Searches can also be conducted without warrants when there are grounds to believe that suspects could flee before a warrant is obtained.
All officers from the three armed services with the rank of sub-lieutenant and higher become crime suppression officers with lower ranks acting as assistants.
They are also authorised officers under the Criminal Code and the Criminal Procedures Code, and their actions are not covered by laws relating to the Administrative Court and Administrative Court Procedure.
They are authorised to take action against a wide range of crimes, including: extortion, abuse of labour, human trafficking, robbery, fraud, document forgery, defamation, debt collection, alien workers, gambling, immigration, child protection, tour guide services, forests, prostitution, excise taxation, price collusion, customs, loan sharking, entertainment venues and firearms.
The offences must involve either coercion, threats or illegal activities.
Regarding powers of the assigned soldiers, they can order individuals to report to them to give evidence connected with their alleged offences.
They can arrest suspects at the scene and take them to inquiry officers for further processing.
They can also assist or join an investigation carried out by inquiry officers.
Deputy Prime Minister Prawit Wongsuwon said Wednesday the move is aimed at thwarting criminals who cause trouble for the public, adding he does not want the public to term it as an anti-mafia operation.
He said military officers would also act as inquiry officers because there are not enough policemen.
The move has nothing to do with police performance, he added.
Bencharat Sae Chua, a human rights and peace studies lecturer at Mahidol University, said the order violates due process.
Legal procedures usually involve the police, prosecutors and the court. However, under Gen Prayut's order, it all comes down to soldiers.
"They can search, arrest and detain without a court warrant," she said.
Furthermore, the list of offences included in the order is too vague and could be interpreted in such ways that would target regime critics, Ms Bencharat added.
On Wednesday, a community leader protesting a government plan to build a waste-to-energy plant in Pathum Thani was arrested under the order.
"The NCPO is returning us to the dark ages," said Yaowalak Anuphan, director of the Thai Lawyers for Human Rights group. "The Thai judicial system has evolved to reach acceptable standards but the military is intent on cutting that process short."