Nhat edged out Kazakhstan's Almaz Sarsembekov 29-28 after three rounds in the final that took place Monday (Hanoi time), claiming the first World Games gold of his career.
With Nhat's victory, Vietnam claimed two gold medals at the 2022 World Games, the first one won by Duong Thuy Vi in wushu last week.
Vietnam finished 31st overall in the medal standings, its best ever achievement at the World Games.
Vietnamese athletes had claimed a gold at the 2009 World Games in Chinese Taipei, a gold and a silver in 2013 in Colombia, and a gold in 2017 in Poland.
World Games is an international multi-sport event that includes sports not included in the Olympics. This event is also hosted every four years, usually one year after the Summer Olympics.
Vietnam competed in four sports at the 2022 World Games - billiards, muay thai, wushu and women's beach handball.
This year's event, featuring 30 sports in 54 disciplines, took place July 7-17 in Birmingham, Alabama.