Thailand, officially the Kingdom of Thailand and formerly known as Siam is a country located at the center of Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the west by the Andaman Sea and the southern extremity of Burma. Its maritime boundaries include Vietnam in the Gulf of Thailand to the southeast and Indonesia and India in the Andaman Sea to the southwest. The country is a kingdom, with most recorded reigns in the world; a constitutional monarchy with King Rama IX, the ninth king of the House of Chakri, who has reigned since 1946, making him the world's longest-serving current head of state and the longest-reigning monarch in Thai history. The king is officially titled Head of State, the Head of the Armed Forces, an Upholder of the Buddhist religion, and the Defender of all Faiths.

Thailand is the world's 50th largest country in terms of total area with a surface area of approximately 513,000 km2 (198,000 sq miles), and the 21st most-populous country, with approximately 64 million peoples. Thailand experienced rapid economic growth between 1985 and 1995 and is a newly industrialized country with tourism, due to well-known tourist destinations such as Ayutthaya, Pattaya, Bangkok, Phuket, Krabi, Chiang Mai, and Ko Samui, and exports contributing significantly to the economy.

Bangkok is the capital, largest urban area and primary city of Thailand. Known in Thai as Krung Thep, meaning "city of angels", it was originally a small trading post on the west bank of the lower Chao Phraya River during the Ayutthaya Kingdom. It became the capital in 1768 after the destruction of Ayutthaya by Burmese invaders. However, the current Rattanakosin Kingdom did not begin until 1782, when the capital was moved to the east bank of the river by Rama I following the death of King Taksin. The city is more formally called "Phra Nakhon", referring to the original boundaries of the 18th century, while the name Krungthep Mahanakorn includes the urban areas which have since grown. Foreigners generally call the city by its original name of Bangkok.