Thailand is about 657 times bigger than New York City.

New York City (including all five boroughs: Manhattan, Brooklyn, Queens, The Bronx, and Staten Island) is approximately 781 sq km, while Thailand is approximately 513,120 sq km, making Thailand 65,600% larger than New York City.
Tip: This to-scale comparison of New York City vs. Thailand uses the Mercator projection, which distorts the size of regions near the poles.