I wouldn't take that list seriously.
It is diffucult to find a website about modern vietnam military, as far as I know they don't even have an official website. I kept getting a vietnam war era website instead.
Anyways....
The vietnam military (all branches included) are the ninth largest in the world. I heard they are uprgrading their naval fleets and are modernizing their T-55 tanks, rumor has it that they are trying to aquire T-72 tanks of unknown model.
Their air force has Mig-21 fighters, Su-22, Su-27, and L39 in their inventory. I believe they are all operational. Russia has also sold them S-300PMU and four fighters Su-30MKK.
Edit- forgot to give you a link to a vietnam naval webiste.
http://www.hazegray.org/worldnav/asiapac/vietnam.htm