BANGKOK -- The Association of Southeast Asian Nations should "delegitimize" the near-certain victory of Cambodian Prime Minister Hun Sen in an election Sunday that may "set the tone" for authoritarianism in the region, a leading human rights politician said Tuesday.

"It is a shame that ASEAN hasn't stood up," Charles Santiago, who chairs the ASEAN Parliamentarians for Human Rights group, said at a teleconference with the foreign correspondents club in Bangkok.

"The international community should not give any form of legitimacy to a sham election," he said.

Santiago, a member of the Democratic Action Party within Malaysia's new ruling coalition, urged ASEAN governments to send no congratulatory notes to Hun Sen, who has ruled Cambodia since 1985, after the election.

Hun Sen's ruling Cambodian People's Party faces no viable competitor following the forced disbanding of the main opposition Cambodian National Rescue Party in November. Following the party's dissolution and the government's crackdown on critical media outlets, Western countries have announced sanctions such as visa bans on high-ranking Cambodian officials and withdrawn funding for the election. But fellow Southeast Asian governments have stayed mum.

Santiago's comments came days after Cambodia took a swipe at Malaysian lawmaker Wong Chen, who called on his country to take "a more proactive stance" against efforts by Phnom Penh seen as undermining free and fair elections. Cambodia cited the 10-member regional bloc's policy of noninterference in the internal affairs of members.

ASEAN's noninterference policy at times prevents the bloc from effectively addressing human rights issues involving member states, such as the military crackdown on the Rohingya Muslim minorities in Myanmar. Yet the 10 member countries signed and adopted the ASEAN Human Rights Declaration at the 2012 summit held in Phnom Penh.

"Countries such as Indonesia, Singapore, Malaysia have to come up to say that what is happening in ASEAN should be consistent to what we are signing," Santiago said. "Otherwise, ASEAN will look very exposed, very undemocratic and, therefore, people will give up and have no faith in the ASEAN process."

Santiago cited an advance of authoritarian rule around Southeast Asia. He noted the Philippines, where President Rodrigo Duterte's "war on drugs" has resulted in thousands of deaths.

In Thailand, the military government has held power for over four years, continually delaying a promised election.

"You can see how the dictators in the region are all colluding with each other," Santiago said, "organizing themselves to stay in power in order to control the wealth in their possession."

ASEAN was formed in 1967 by Indonesia, Malaysia, the Philippines, Singapore and Thailand. Cambodia joined in 1999. It was originally slated to join in 1997 but ASEAN suspended Cambodia's membership after Hun Sen, then holding the position of second prime minister, staged a coup to oust the first prime minister that year.