South Dakota is around the same size as Cambodia.

Cambodia is approximately 181,035 sq km, while South Dakota is approximately 196,540 sq km, making South Dakota 9% larger than Cambodia. Meanwhile, the population of Cambodia is ~16.7 million people (15.9 million fewer people live in South Dakota).
Tip: This to-scale comparison of Cambodia vs. South Dakota uses the Mercator projection, which distorts the size of regions near the poles.