District of Columbia is about 2,899 times smaller than Thailand.

Thailand is approximately 513,120 sq km, while District of Columbia is approximately 177 sq km, making District of Columbia 0.03% the size of Thailand. Meanwhile, the population of Thailand is ~69.6 million people (69.0 million fewer people live in District of Columbia).
Tip: This to-scale comparison of Thailand vs. District of Columbia uses the Mercator projection, which distorts the size of regions near the poles.