Nam did not compete in an international tennis tournaments in the past week. He now has 48 points.
Vietnam’s No 2 player, Nguyen Hoang Thien, also dropped eight spots from world No 1,539 to 1,601, with only two points.
Additionally, Vietnamese representative Trinh Linh Giang slid 23 steps from world No 2,049 to 2,072 with only one point.
In the men’s doubles rankings, Nam also dropped two places from world No 619 to 621. Meanwhile, Nguyen Hoang Thien rose two slots to world No 784.