(Reuters) - Thai police have arrested a man convicted of involvement in a bomb attack in India two decades ago that killed 18 people, including the then-chief minister of Punjab, a spokesperson said on Tuesday.

Gurmeet Singh, also known as Jagtar Singh Tara, a former member of the Babbar Khalsa International Sikh separatist group, was jailed for life in 2007 for his involvement in the 1995 attack outside a government complex in Chandigarh.

A bomb planted in then-Chief Minister Beant Singh's car exploded killing Singh and 17 others, including aides and members of his security detail.

Singh was one of six militants convicted in connection with the blast.

He and three others escaped a high-security prison in India in 2004. Singh entered Thailand in October, police said, and was arrested in the seaside town of Pattaya, east of the capital Bangkok, on Monday.

"We arrested fugitive convict Mr. Gurmeet Singh in Pattaya after monitoring his movements for several months and with the help of police in India," Royal Thai Police spokesman Police Lieutenant General Prawut Thavornsiri told Reuters.

Police were seeking permission from Thailand's Supreme Court to extradite Singh, he added.

"The plan is to send him back to India."

Beant Singh became chief minister of Punjab in 1992.