Despite sweeping economic reform and increasing openness to social change, Vietnam's ruling Communist Party retains tight media censorship and does not tolerate criticism.
A district court found Doan Khanh Vinh Quang, 42, guilty of "abusing democratic and freedom rights" to infringe the interests of the state, individuals, and organizations, police in Can Tho City said on Monday.
Quang's actions "seriously affected the political security and social order and safety", the police said in a statement, adding that he had admitted to having written and shared posts insulting the Party and the country since 2015.
He was arrested in early September as authorities found his Facebook posts "distort the guidelines and policies of the party and the state" and called for people to protest, they said on their website.
Reuters could not trace contact details for Quang's lawyer to seek comment.
Facebook has a direct channel for Vietnam's information ministry to request the blocking or removal of accounts, content or posts deemed to violate the law. Many activists have complained about growing blocking of content this year.
Not all the ministry's requests are met, however, and acting information minister Nguyen Manh Hung this month proposed to set up a working group to improve communications between the government and Facebook.
Police said Quang also received two flags of the U.S.-backed Republic of Vietnam, the former state in the country's southern half until the Vietnam War ended in 1975, from another Facebook user living overseas and agreed to hang them.
They added that Quang uses Facebook to urge people to turn out for street demonstrations against a controversial draft law to develop economic zones against which thousands had protested in several cities in June.