The capital of the country is Bangkok.

An excerpt from the article 31 facts about Thailand

It is also the largest city in Thailand, located at the mouth of the Chao Phraya River (the main river of Thailand) into the Gulf of Thailand. About 5.6 million people live there, and about 15 million in the entire agglomeration.

Bangkok is one of the world's most popular tourist destinations. In 2018, it was visited by approximately 22 million tourists - it was the most visited city in the world.