Bowatte Indraratana died over the weekend after setting himself on fire Friday near the famed Temple of Buddha's Tooth Relic in the central town of Kandy, demanding ban on cow slaughter.
He was also demanding that parliament should approve the anti-conversion bill to prevent mainly Sinhalese Buddhists being converted into other religions.
The monk was a member of the Sinhala Ravaya (Voice of Sinhala), a hardline Buddhist rights group which said Indraratana was long frustrated by inaction over the demand to ban cattle slaughter.
Wijayadasa Rajapaksha of the main opposition UNP said that a private members' motion presented by him in 2009 to ban cattle slaughter was ignored by parliamentarians.
"I hoped the Buddhist and Hindu MPs would support it. No one did. Now after the self immolation people see the need to it", Rajapaksha said.