By Agence France-Presse
The footage, which emerged earlier this week, shows the two-year-old screaming and crying as a man prods different parts of his body with the stun gun and later shoves an object down his throat.
A Vietnamese man, 34-year-old Nguyen Thanh Dung, was arrested in Ho Chi Minh City on Wednesday and confessed to abusing the boy in an interview published by state media.
He told investigators he was high on meth when he carried out the abuse in Cambodia in August.
On Friday his partner Stefan Struik, a 53-year-old Dutch national who also holds Cambodian citizenship, was charged with failing to report the crime.
"The court charged and jailed him for failing to file a complaint about the mistreatment of the minor and for hiding leads," said Meas Pros, a spokesman for the court in northeastern Mondulkiri province.
Dung will be prosecuted in Vietnam, he added.
According to James McCabe, who heads the Child Protection Unit and is assisting with the investigation, Dung was asked to care for the two-year-old boy while his parents worked on Struik's farm in Cambodia.
The child is now safe and with his family in Phnom Penh, said McCabe.
The video also became a source of outrage in nearby Myanmar this week after the UK's Daily Mail cited false reports that it showed a Burmese soldier torturing a Muslim Rohingya child.
Myanmar's government lambasted the article, which the British tabloid later took down without apology, and claimed it as evidence that foreign media have been distorting information about a military crackdown on the Muslim minority.
The country is facing mounting international pressure to probe allegations that its soldiers are carrying out atrocities against the Rohingya in western Rakhine state, an area off-limits to journalists and rights groups.
More than 20,000 Rohingya have fled the crackdown to Bangladesh since October, carrying with them stories of mass rape, murder and arson by soldiers.
Myanmar officials have denied the allegations and blamed the reports on "fake news" circulated by activists with a political agenda.
In a statement Friday, the office of de facto leader Aung San Suu Kyi slammed the Daily Mail story as "only the latest example of fabricated news coverage that has damaged the country's image".