In recent years, transit routes in Vietnam for drug trafficking networks in the Southeast Asia region and beyond have expanded considerably. Many international scholars are working on identifying destination and transit routes of drug trafficking entities “to and through” Vietnam. Among these routes, the crossings through the Vietnam–Laos borderland of about 2,340 km are among the most severe concerns. This article analyses supply-and-demand scales of illicit drugs in Vietnam from 2008 to 2017 within the context of illegal drug trafficking in the mainland Southeast Asian region. Some evidence consistent with the “destination and transit route” arguments were found through mapping three main ways across the Vietnam–Laos borderland. The article also calls for enhancing the bilateral cooperation among law enforcement agencies to prevent and combat drug trafficking from the two sides.