On Monday a murder charge was unexpectedly withdrawn against the Indonesian woman accused alongside her, sparking calls from Vietnam for Huong to be freed and prompting her lawyers to apply for her release.
"We regret the fact that the Malaysian court did not set free Doan Thi Huong immediately", foreign ministry spokeswoman Le Thi Thu Hang said, urging a fair trial.
Responding to news about the AG's rejection of the application from Vietnamese Doan Thi Huong's lawyers for a withdrawal, the DAP national legal bureau chairman said it raised questions about the AG's absolute power to decide prosecutions in the country.
Vietnam's ministers of justice and foreign affairs are communicating with their Malaysian counterparts to secure his client's release, Teh added.
"Malaysia will create a thorny bilateral problem with Vietnam if there is no similar treatment", said Bridget Welsh, a Southeast Asia expert with John Cabot University in Rome.
Huong and Siti, 27, were charged with the murder of Kim Jong Nam in the concourse area of the Kuala Lumpur International Airport by smearing his face with a toxic nerve agent and the court ruled last August that there was sufficient evidence for the case to proceed. Both the accused stated through counsel that they were doing pranks. They were the only people in custody after four North Korean suspects fled the country the same morning Kim was killed.
Prosecutors did not reveal why they rejected Huong's appeal but let Aisyah go free.
Analysts said Aisyah's release was in part due to politics and the improved relations between Indonesia and Malaysia that have come since Mahathir Mohamad returned to the Malaysian premiership past year after the stunning election defeat of Najib Razak. "Mahathir knows how important good ties are and in this more open era, supporting democratic allies is essential", Welsh said. The government vowed past year to scrap capital punishment but has indicated recently it may water down the plan and only do away with the mandatory death penalty. It also seized a luxury yacht at the centre of a Malaysian corruption scandal off Bali island in co-operation with U.S. Federal Bureau of Investigation and returned it to Malaysia past year. "Her case is the same as Siti Aisyah's".
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Teh rejected speculation that Siti Aisyah's release was due to a lack of video evidence against her, saying the court had already established a case against both.
Lawyers for both women argued that they were pawns in a political assassination with clear links to the North Korean Embassy in Kuala Lumpur.
The duo had been charged over the murder.
The North denies the claim.
Indonesia's government has said its continual high-level lobbying resulted in Aisyah's release.
"She was taken to the psychiatric ward.it was just a physical and mental examination", Salim said when contacted by Bernama. She thanked the Party, State and the Vietnamese Embassy in Malaysia for their help and support.
It is thought that diplomatic pressure from Indonesia, in particular President Joko Widodo who is facing an election next month, contributed to the Malaysian government's decision to drop the charges against Siti.