Since the Inaugural Edition of AFC Asian Cup which was founded in 1956 Vietnam football Team only qualify for the Three Asian cup football tournament in 1956, 1960, 2007 So this is the Fourth Appearance in the Asian Cup for Vietnam in 2019 Edition.
If we look at the Recent Times performance of Vietnam in Asian Cup then Best performance in the 2007 where they ended as a Quarter Final.

Vietnam football players
Upcoming 2019 AFC Asian Cup Vietnam team drawn in the Group A thus they face to Iran, Iraq, Yemen in the group stage. Vietnam Team Asian cup campaign starting on 8th January 2019 when they face to Iraq at Zayed Sports City Stadium, Abu Dhabi.
Vietnam Performance in Asian Cup
1956 – Fourth Place
1960 – Fourth Place
2007 – Quarter Finals