Vietnam is 3.3 times larger than Korea (South).
Area: 99,720 km2 World Factbook
Population: 49,039,986 (July 2014) World Factbook
South Korea, officially the Republic of Korea, is a country in East Asia, constituting the southern part of the Korean Peninsula. The name Korea is derived from Goryeo (also spelt Koryo), a dynasty which ruled in the Middle Ages. Wikipedia
Area: 331,210 km2 World Factbook
Population: 93,421,835 (July 2014) World Factbook
Vietnam, officially the Socialist Republic of Vietnam, is the easternmost country on the Indochina Peninsula in Southeast Asia. With an estimated 90.0 million inhabitants as of 2013, it is the world's 13th-most-populous country, and the eighth-most-populous Asian country. Wikipedia