The Crime Suppression Division (CSD) is leading the investigation into the match-fixing football scandal, according to CSD acting chief Maitree Chimcherd, with a high-profile ex-referee singled out as the mastermind.
The CSD will be responsible for gathering evidence in the case, as instructed by national police chief Pol Gen Chakthip Chaijinda.
Pol Col Maitree said the investigation team includes Pol Col Somkwan Phuengsap, the CSD deputy commander.
The CSD is assuming a leading role in the probe as the wrongdoing took place in many locations. Pol Gen Chakthip said earlier the suspects were part of a "large network spread over the country".
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But the task of collecting detailed facts needed to enlarge the probe into related offences rests with the Metropolitan Police Bureau (MPB).
The CSD and MPB will work in tandem under the supervision of the national police chief.
A police source said that before the scandal unfolded on Tuesday, the police had assigned a special team that had been working for a year on a covert operation linked to the case.
Twelve suspects have been arrested including five professional players, one referee, a linesman, a member of one of the club's management teams and four business people, according to the source.
Four of the players are from top-flight team Navy while the other hails from Nakhon Ratchasima in the same domestic league.
The source said investigators have identified a former referee, who is well-known nationally, as the match-fixing mastermind. His name was not disclosed.
The source said three or four suspects -- comprising players and business people involved in football betting -- have admitted to helping fix matches.
He said authorities are now tracing the money trails to gather evidence that would be of more use to prosecutors.
The others have reportedly denied all involvement in the scam, which he said has damaged the image of Thai football.
Pol Gen Chakthip said on Tuesday the suspects colluded to fix the results of games last season. The men were arrested and released on bail after a year-long probe, Pol Gen Chakthip said.
The 12 suspects are accused of "receiving money or benefits in order to throw a game or influence others to throw a game or manipulate the score".
The source said the games were fixed for gambling rather than seeking to win trophies.
The illegal fixes generated 2-3 million baht per match, the source said, putting the mastermind's cut at 100,000 baht.
The MPB's investigation division chief Itthipol Atchariyapradit said no more suspects are being investigated and no players from the national team are known to have colluded in the scam.
The probe found foreign elements supported the ring, he said. The probe is due to wrap up in a month.