Tara's, 37, custody was obtained from the Thai Police. He had escaped 10 years ago from Chandigarh's Burail jail by digging a tunnel.
He will be produced before a court in Patiala where police may press further charges against Tara under Unlawful Activities (Prevention) Act (UAPA) as he was staying in Thailand on a Pakistani passport, official sources said.
His interrogation may throw light on Pakistan's notorious snooping agency ISI's attempts to revive Sikh militancy in India.
Tara, 40, had been staying in Pakistan and had entered into Thailand on a passport issued from Islamabad authorities as Gurmeet Singh.
He had been shifting from one place to another before being nabbed by Thai police on January 5 this year following an Interpol Red Corner Notice issued against him.
India had been pressing for his deportation but the Thai Police produced him in the court as he had been arrested on a Pakistani passport.
After his extradition order by a Thai court on January 7, no other appeal of Tara was entertained as India established Tara's identity beyond doubt that he was the same person who had been convicted in absentia for Beant Singh's assassination case in 2007, 3 years after he had fled.
According to CBI, Tara was directly involved in the assassination of Beant Singh as he had purchased the car which was used to kill the then CM in Chandigarh secretariat.
Indian agencies, Thai police and Interpol tracked Tara in Thailand and arrested him in Chonburi province in Pattaya. He was a member of militant group Babbar Khalsa International at the time of the assassination of Singh, but later joined Khalistan Tiger Force.
Tara had escaped from jail in 2004 along with Jagtar Singh Hawara, Paramjit Singh Bheora and Dev Singh.
Hawara and Bheora were later arrested but Tara and Dev Singh reportedly fled to Pakistan. Dev Singh is believed to be still living in Pakistan. Tara left for Thailand after hiding in Pakistan for many years.
Image: Babbar Khalsa militant Jagtar Singh Tara