Opponents of the newly approved Peaceful Society Promotion Bill should accept the majority decision, says Adul Khiewboriboon, chairman of the Committee of Relatives of the Black May 1992 Heroes.
He made the remarks on Sunday following parliament's approval of the bill, saying no side can get everything it wants in a democracy.
The bill passed after the Senate amended the version approved by the House, removing a provision granting amnesty to people under the age of 18 charged under Section 112, the lese-majeste law.
The revised bill cleared parliament with 307 votes in favour and 141 against, and is now awaiting royal endorsement before publication in the Royal Gazette.
Mr Adul thanked all members of parliament for participating in the debate, regardless of how they voted.
"Those who supported the bill and those who opposed it all acted with good intentions for the country, even if they held different opinions," he said.
Political demonstrators from opposing camps had also acted out of what they believed to be the national interest, he added.
He said the original draft had been framed as an amnesty bill but was later renamed the Peaceful Society Promotion Bill to better reflect its purpose.
Parliament has the authority to enact such legislation but cannot grant amnesty for Section 112 offences because doing so would conflict with the constitutional powers of the monarchy, he said.
People facing lese-majeste charges should instead seek a royal pardon through the established legal process, he argued.
Most people under the age of 18 accused of Section 112 offences have already completed rehabilitation through the Juvenile and Family Court system, Mr Adul added.
It is an internationally accepted principle that corruption cases involving former national leaders should not be covered by blanket amnesties, he said.
He cited South Korea as an example, where former presidents convicted of corruption were pardoned by the country's head of state to reduce political conflict, although public protests continued.
He acknowledged some groups remained disappointed the bill excluded Section 112 cases, but insisted the compromise must be accepted. "If opponents reject the entire bill simply because it does not include Section 112 offences, more than 6,000 people from all political camps will remain tied up in legal proceedings and the seeds of conflict will remain," he said.
"In a democracy, no side gets everything it wants. The minority must accept the majority's decision. Thailand is facing serious challenges, so everyone should look ahead and work together to build a peaceful society," he added.
