PHNOM PENH: Unable to pay his way out of jail, Kong Chamroeun was remanded in a Cambodian prison pending trial for stealing $80 of company property, a crime his family said he did not commit.

"We had nothing, just empty hands," said his girlfriend, Lorn Chenda, who alleged police tried to extort Chamroeun for $2,000 in "compensation" in exchange for not pressing charges.

With Chamroeun (28) behind bars for 10 days and no one else to turn to, Chenda used her smartphone to appeal directly to Cambodia's highest authority - Prime Minister Hun Sen.

She recorded a five-minute video detailing the alleged extortion attempt and urging the self-styled strongman to intervene, then posted it on his Facebook page.

The next morning, Chamroeun was freed and his case dismissed.

"We never expected the prime minister would help us," Chenda (26) told Reuters.

"This is the smallest problem for the prime minister to have to solve himself, and it was solved very quickly."

Chamroeun's release was fortuitously timed, coinciding with Hun Sen's new infatuation with Facebook, which he adopted with gusto in September last year and now has two million followers.

Experts say he is using Facebook to quickly recoup some lost popularity ahead of a 2018 election tipped to be the biggest test to his three-decade rule.

Hun Sen's strategy appears to be out of the playbook of bitter rival the Cambodia National Rescue Party (CNRP).

The opposition's social media campaigns were a hit with young, urban voters in a disputed 2013 election that stunned Hun Sen's ruling Cambodian People's Party (CPP) and sharply reduced its house majority.

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Chenda's video appeal to Hun Sen went viral and the premier has since urged the public to send complaints about government corruption to his Facebook inbox.

He referred to Chamroeun's case at a recent speech, adding that without Facebook, he could not serve the public so effectively.

"I need to have work done quickly," he said. "The problems the people face are not small, do not underestimate them."

It was not an isolated case. The former Khmer Rouge soldier has been credited with solving numerous problems raised on his Facebook, like high university test fees, informal road tolls and issues with motorcycle licenses and inheritance tax.

Seven ministries have set up working groups with 64 members who trawl postings on Prime Minister Hun Sen's Facebook page looking for solvable public grievances, including land disputes, arguably Cambodia's most entrenched problem.

"We track the comments all the time, every day," said Seng Loth, who monitors the page for the Land Management and Urban Planning Ministry.

"This is at the direct instruction of the prime minister so this work can't be ignored."

The government last year held mandatory classes for 400 heads of Phnom Penh schools, where they were encouraged to use Facebook and write messages supportive of the CPP.

Sebastian Strangio, author of the book, "Hun Sen's Cambodia", said successes from using Facebook to troubleshoot voter problems were being spun as Hun Sen's "personal gifts" to the public and ignored the need for structural reforms to tackle graft, injustice and bureaucratic inefficiency.

"This populist strategy merely reproduces an old pattern in Cambodian politics, which is that improvements in people's lives are treated as a blessing from the powerful, rather than as part of a democratic social contract," Strangio said.