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

District of Columbia is approximately 177 sq km, while Thailand is approximately 513,120 sq km, making Thailand 289,798% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (69.0 million more people live in Thailand).
Tip: This to-scale comparison of District of Columbia vs. Thailand uses the Mercator projection, which distorts the size of regions near the poles.