Vang A Thenh, 20, and Ho A Manh, 20, were caught transporting the drugs via a pick-up truck on a National Highway 1A section through Bo Trach District on Tuesday, police stated.
Thenh and Manh said they were hired for VND300 million ($12,820) to transport the 15 bags from a Laos border gate in the neighboring Ha Tinh Province to Saigon.
Further investigations led to the arrest of Nguyen Van Thang, 26, and Dinh Ngoc Do, 42. Hong Van Pao, 46, is currently on the run.
Vietnam is a key trafficking hub for drugs from the Golden Triangle, an intersection of Laos, Thailand and Myanmar and the world's second largest drug producing area after the Golden Crescent in South Asia.
Though it has some of the world's toughest drug laws, including death for smuggling and trading, drug busts are frequent.
Those convicted of possessing or smuggling over 600 grams of heroin or more than 2.5 kilograms of methamphetamine face capital punishment. The production or sale of 100 grams of heroin or 300 grams of other illegal narcotics is also punishable by death.