Thailand, officially the Kingdom of Thailand, and formerly known as Siam until 1939, is a country located in mainland Southeast Asia. It shares land borders with Myanmar to the west and northwest, Laos to the east and northeast, Cambodia to the southeast, and Malaysia to the south. Its maritime boundaries include the Gulf of Thailand and the Andaman Sea, as well as maritime borders with Vietnam, Indonesia, and India. Thailand has a population of nearly 66 million people, covers an area of approximately 513,115 km (198,115 sq mi). The country's capital and largest city is Bangkok.
Archaeological evidence indicates that humans have inhabited the area of present-day Thailand for at least 40,000 years. Indigenous ethnic groups include the Mon, Khmer, and Malay people. The Tai people are believed to have originated from the Điện Biên Phủ region since the 5th century and began migrating into the territory of modern Thailand between the 8th and 10th centuries origin of the Tai people. During the classical historical period, major kingdoms such as Sukhothai, Lan Na, and Ayutthaya were established. The Sukhothai Kingdom is regarded as the beginning of Thai history, while the Ayutthaya Kingdom, founded in 1350 CE, became a regional power replacing the Khmer Empire. European contact began in 1511 CE when Portuguese envoys arrived in Ayutthaya. The Ayutthaya Kingdom flourished until its complete destruction during the 1765–1767 Burmese–Siamese War by the Burmese forces under the Konbaung dynasty in 1767.