According to the FreedomHouse report in 2018, Vietnam does not have freedom of speech. More than 200 journalists, bloggers, and activists were imprisoned due to expressing views that do not align with what the government says.
You can be punished for opposing the government’s views, cannot vote for your own government, there is no free and objective media, and that’s just a few examples. All the censorship, control, and government snooping add up to the so-called Bamboo Firewall.