The four, three women and one man, aged between 21 and 28, were apprehended near the Vietnam-Laos border in Khammouane Province, about 74.8 km to the west of Vietnam's Cha Lo border gate.
Vietnamese and Lao authorities confiscated 60,000 ecstasy pills and ฿10,000 ($329) in cash.
Vietnam is a key trafficking hub for narcotics from the Golden Triangle, an intersection of China, Laos, Thailand, and Myanmar and the world's second largest drug producing region after the Golden Crescent in South Asia.
Drug trafficking and consumption have worsened in Vietnam over the last few years though it applies some of the world's toughest laws, including capital punishment for producing and smuggling banned substances.
Those convicted of possessing or smuggling over 600 grams of heroin or 2.5 kilograms of methamphetamine face the death penalty. The production or sale of 100 grams of heroin or 300 grams of other illegal narcotics is similarly punishable.