Pham Chi Dung, 53, is facing charges for fabricating, storing, and disseminating information as well as other materials opposing the Vietnamese government. Some of his public actions "seriously violated the law" and was "very dangerous" to public order, HCMC police said in a statement.
The investigation into Dung’s actions imperative and in accordance with the law, they said.
Several documents have been seized to serve the investigation, the police added.
Dung was put under investigation with similar allegations in 2012.
If found guilty, he could face a jail sentence of five to 20 years.