The Vietnamese football team has lost 89 points and is now placed 146th in the world, according to the latest FIFA rankings for August.
The team has not played any matches after a series of friendlies last June.
Meanwhile, its rival Thailand reclaimed the highest position in the Southeast Asian region jumping to 133rd place following successes over the last eight months.
Spain still dominates the rankings followed by Germany. The UK made the only change in the top ten beating Uruguay to finish third.
Japan still tops the Asian list at 22nd, with Australia and the Republic of Korea coming close behind.
The next FIFA rankings will be announced on September 5./.