Cambodian leader Hun Sen on Tuesday ordered election laws to be changed to ban anyone who fails to vote in an upcoming poll from ever running for office -- a move that will affect exiled rivals.

The kingdom votes in a general election next month with Hun Sen's party running almost unopposed, after the main opposition outfit was barred on a technicality.

Rights groups accuse Hun Sen, who has ruled Cambodia for nearly four decades, of using the legal system to crush any opposition to his power.

Hun Sen said he had asked officials to add a clause to election laws saying that anyone who does not vote in the upcoming poll has no right to run in future ballots.

"If you don't vote on July 23, 2023, you will have no right to be elected" in any future elections, Hun Sen said in a speech to thousands of garment workers in Phnom Penh.

The change will take effect in time for the election, he said.

The move will largely affect the many leading opposition figures who have fled the country to avoid convictions they say are politically motivated.

Hun Sen said he was forced to make the amendment to counter calls for an election boycott by opposition activists after the main opposition Candlelight Party was disqualified for the July polls.

The party was barred by the National Election Committee last month after it failed to submit certain documents as part of the registration process.

Hun Sen, already one of the world's longest-serving leaders, is aiming to extend his rule before passing the leadership on to his son Hun Manet.

Scores of opposition politicians have been convicted during his time in power.

Opposition leader Kem Sokha was sentenced in March to 27 years in prison and placed under house arrest for treason over an alleged plot with foreigners to topple Hun Sen's government.

Another opposition figure, Sam Rainsy, has been living in exile in France since 2015 to avoid prison for convictions he says are politically motivated.

AFP