South Korea is about 3.1 times smaller than New Mexico.

New Mexico is approximately 314,310 sq km, while South Korea is approximately 99,720 sq km, making South Korea 31.73% the size of New Mexico. Meanwhile, the population of New Mexico is ~2.1 million people (49.8 million more people live in South Korea).
Tip: This to-scale comparison of New Mexico vs. South Korea uses the Mercator projection, which distorts the size of regions near the poles.