Cambodia is about 2.1 times smaller than Montana.

Montana is approximately 376,979 sq km, while Cambodia is approximately 181,035 sq km, making Cambodia 48.02% the size of Montana. Meanwhile, the population of Montana is ~989,415 people (15.7 million more people live in Cambodia).
Tip: This to-scale comparison of Montana vs. Cambodia uses the Mercator projection, which distorts the size of regions near the poles.