Hoang, a gold medalist at the 2015 SEA Games, fought Arthit Bunphloeang in the World Boxing Association (WBA) Asia middleweight category.
Hoang quickly floored his opponent with a flurry of punches early in the first half. Bunphloeng was defensive and repeatedly clinched his opponent.
With five seconds left in the first round, Hoang threw a right that knocked out his opponent.
Hoang later told VnExpress: "My goal is to win a professional boxing belt. In the coming time, I will attend other matches in preparation for the upcoming SEA Games 30 scheduled from November 30 to December 10."
The WBA is one of four major boxing organizations along with the IBF, WBC and WBO. The WBA Asia Championship is one of the most prestigious boxing competitions on the continent.
Many Vietnamese fans had also been keenly looking forward to the fight between World Boxing Council Asia champion Tran Van Thao and higher ranked Chinese boxer Rongguo Wu on Saturday.
But Thao pulled out at the last minute after injuring his leg in a road accident.