Opposition figures in Southeast Asian nations, some locked out of government for decades, celebrated Mahathir Mohamad's unexpected election victory in Malaysia this week, and said they hoped it was a portent of wider democratic change in the region.

Rising authoritarianism across Southeast Asia has alarmed human rights advocates and analysts in recent years as governments imprisoned rival leaders, manipulated election laws and restricted freedom of the press and civil society.

"The vote marks a bright spot amid dark times," said the Asean Parliamentarians for Human Rights, a grouping of Southeast Asian politicians.

Mahathir defeated Malaysia's ruling coalition of more than six decades despite a drastic redrawing of electorate boundaries and media coverage strongly favouring the incumbent.

"What the Malaysian people have achieved is very encouraging for us," the chairman of Cambodia's outlawed main opposition party, Sam Rainsy, told Reuters by phone from the United States.

"It shows this is possible in Cambodia as well." Thailand's exiled former prime minister Thaksin Shinawatra, who was deposed by the military in 2006, also welcomed the election result as evidence of "the power of the people".

Cambodia, ruled by strongman Hun Sen for more than three decades, and Thailand, governed by a military junta after another coup in 2014, are both due to go to the polls in the next 12 months.

Repression risks

Lee Morgenbesser, an Australian academic who studies Southeast Asian regimes, cautioned that the Malaysian election could lead to more repression rather than a regional democratic awakening.

"If you have this stunning election result, it sends a warning to authoritarian regimes in the region," he said.

"That might actually reinforce the trend that's been happening for years. You just could see more suppression and manipulation at election time."

He cited the example of the Arab Spring in the Middle East that began in 2010. Early democratic gains were reversed as rulers responded aggressively, often with brutal violence and arbitrary arrests of dissidents.

Thailand has had 12 successful coups since 1932. The current junta has postponed elections and banned public gatherings of more than five people.

Thailand's military says it seized power to end political turmoil and corruption. The gatherings ban is needed to maintain national security and the election delays are required to give time for new election laws to be formulated, it has said.

'Eliminating competition'

Morgenbesser said Cambodia, meanwhile, "was eliminating competition from the election arena entirely" after last year outlawing the Cambodian National Rescue Party (CNRP) and detaining its leader, Kem Sokha. Independent media outlets have also been forced to close in the past year.

Hun Sen has said the CNRP was dissolved and Sokha arrested after they colluded with the United States to overthrow his government. The CNRP and Sokha's lawyers deny the charges.

"We admire Mahathir's effort to challenge his (former) party's embattled incumbent and win a surprise victory," Huy Vannak, Cambodia's undersecretary of state at the Interior Ministry, told Reuters on Friday.

Rainsy said Hun Sen would win the July election if the CNRP was not reinstated but Cambodians would express their displeasure by refusing to vote. The CNRP has called for a boycott of the poll.

A low turnout would sap the government's legitimacy, he said. "It cannot survive without legitimacy".

Singapore, ruled by the People's Action Party since its independence 57 years ago, has political parallels with Malaysia, analysts said.

The city-state has tough defamation laws that critics argue have been used to quash political opposition. It also has a strongly pro-government media.

"Like Malaysia, it has competitive but flawed elections," said Morgenbesser. "Unlike Malaysia, it doesn't have a major corruption scandal."

Former government lawmaker Inderjit Singh said Singaporeans were "shocked" by the result in Malaysia.

"The immediate reaction among some is that it could happen in Singapore too," he said. "But I don't see Singaporeans ready to change to an opposition government until they can see potential national leaders emerging."

The leader of Singapore's opposition Workers' Party, Pritam Singh, did not respond to requests for comment. The party holds six parliament seats, compared to the government's 80.

- Reuters