The female accomplice was identified as Saowanee Insa.

The police investigation is seeking to determine if there were more accomplices in the case, which cost AIS up to Bt8.5 million.

Pol Sub Lt Manoon Kumuang, an inspector at Bang Sue Police Station, alleged yesterday that Saowanee provided the hacker with more than 6,000 cellphone numbers owned by people who wanted more airtime.

She was said to have collected money from the mobile owners when they received extra airtime illegally.

"She then paid the hacker," Manoon alleged. The officer said Saowanee would be summoned to hear the charges against her.

The alleged hacker, Taweesap Lalitsasiwimol, was yesterday detained at the Criminal Court pending the probe into his alleged hacking of AIS.

At the time he allegedly broke into AIS's system, Taweesap was already on bail pending a review by public prosecutors on his alleged hacking into the Orange network. Two years ago, True Corp Plc, which operates Orange cellphone services, lost more than Bt105 million in a similar sting. Taweesap denied any wrongdoing.

Police asked the court yesterday to detain Taweesap, also known as "Phumipat", out of concern that the suspect would try to tamper with electronic evidence.

"He has computer expertise and evidence is in the computer system," Manoon said. He feared Taweesap might also commit hacking crimes again if allowed on bail.

"We will question 10 more witnesses," Manoon said.

According to a document submitted to the court, AIS was alerted to an advertisement in early February that offered Bt600 worth of airtime at Bt300 for its pre-paid users. Investigations later found that a hacker had got into the AIS system and modified information on allowances granted to many pre-paid users.

AIS lodged a complaint with the police on Monday.

A Crime Suppression Division source said yesterday many financial institutions had contacted police to get more information on Taweesap.

"They suspect that this man might have hacked into their systems before," the source said.

Security agencies from various countries had also requested more information on the case.

Taweesap's alleged hacking of the Orange network earned him an entry in a book on the world's wittiest thefts.

When he was arrested in 2005, he reportedly demonstrated his ability to hack into the system of a world-famous agency that supposedly had a high level of protection.