Throughout the era of Western imperialism in Asia, Siam remained the only state in the region to avoid colonisation by foreign powers, although it was often forced to make territorial, trade, and legal concessions in unequal treaties.

Since the 2000s, the country has been in continual political conflict between supporters and opponents of twice-elected Prime Minister of Thailand Thaksin Shinawatra, which resulted in two coups (in 2006 and 2014), along with the establishment of its current constitution, a nominally democratic government after the 2019 Thai general election, and large pro-democracy protests in 2020–2021, which included unprecedented demands to reform the monarchy.

[iv][23]: 8 The ancient Khmers used the word Siam to refer to people settled in the west Chao Phraya River valley surrounding the ancient city of Nakhon Pathom in the present-day central Thailand; it may probably originate from the name of Lord Krishna, which also called Shyam, as in the Wat Sri Chum Inscription, dated 13th century CE, mentions Phra Maha Thera Sri Sattha [th] came to restore Phra Pathommachedi at the city of Lord Krishna (Nakhon Pathom) in the early era of the Sukhothai Kingdom.

[41][42] However, mainland Southeast Asian sources from before the fourteenth century primarily used the word Syam as an ethnonym, referring to those who belonged to a separate cultural category different from the Khmer, Cham, Bagan, or Mon.

As a result, several Tai city-states were established, scattered from Điện Biên Phủ in present-day northwestern Vietnam and highland Southeast Asia to northeastern India.

[52]: 5, 9  However, several modern geology and archaeology studies found that its centre, Yonok Nahaphan, dates from 691 BCE–545 CE;[52]: 7 [53][54][55] this roughly coincides with the establishment of Shan States, another Tai's federated principalities in the present-day northeast Myanmar.

[34]: 52–3 The earliest conflict between Tai people and the preexisting ethnics was recorded in the mid-4th century when the ruler of Singhanavati, Pangkharat [th], forcibly lost the seat at Yonok to King Khom from Umongasela (present-day Fang).

[78] After Chenla sieged Funan and moved the centre to Angkor, both Siamese Mon and the Angkorian eventually marched the troops to attack Vijaya of Champa in 1201 during the reign of Jayavarman VII, as recorded in the Cho-Dinh inscription (C.3).

Borommatrailokkanat brought about bureaucratic reforms which lasted into the 20th century and created a system of social hierarchy called sakdina, where male commoners were conscripted as corvée labourers for six months a year.

[82]: 186 After a bloody period of dynastic struggle, Ayutthaya entered what has been called the Siamese "golden age", a relatively peaceful episode in the second quarter of the 18th century where art, literature, and learning flourished.

The former capital was occupied by the Burmese garrison army and five local leaders declared themselves overlords, including the lords of Sakwangburi, Phitsanulok, Pimai, Chanthaburi, and Nakhon Si Thammarat.

In his final years there was a coup, supposedly caused by his "insanity", and eventually Taksin and his sons were executed by his longtime companion General Chao Phraya Chakri (the future Rama I).

[82]: 308  In the reign of Mongkut (1851–1868), who recognised the potential threat Western powers posed to Siam, his court contacted the British government directly to defuse tensions.

[89] The unexpected death of Mongkut from malaria led to the reign of underage King Chulalongkorn, with Somdet Chaophraya Sri Suriwongse (Chuang Bunnag) acting as regent.

The combined results of economic hardships brought on by the Great Depression, sharply falling rice prices, and a significant reduction in public spending caused discontent among aristocrats.

[100] The 2004 Indian Ocean earthquake and tsunami hit the country, mostly in the south, claiming around 5,400 lives in Phuket, Phang Nga, Ranong, Krabi, Trang, and Satun, with thousands still missing.

The north of the country is the mountainous area of the Thai highlands, with the highest point being Doi Inthanon in the Thanon Thong Chai Range at 2,565 metres (8,415 ft) above sea level.

The Gulf of Thailand covers 320,000 square kilometres (124,000 sq mi) and is fed by the Chao Phraya, Mae Klong, Bang Pakong, and Tapi Rivers.

[122]: 3 Due to their inland position and latitude, the north, northeast, central and eastern parts of Thailand experience a long period of warm weather, where temperatures can reach up to 40 °C (104 °F) during March to May,[122]: 3  in contrast to close to or below 0 °C (32 °F) in some areas in winter.

Some academics outside Thailand, including Duncan McCargo and Federico Ferrara, noted extraconstitutional role of the monarch through a "network monarchy" behind the political scenes.

[159] Thailand is a unitary state; the administrative services of the executive branch are divided into three levels by National Government Organisation Act, BE 2534 (1991): central, provincial and local.

[163] During the Cold War, Thailand sought to prevent the spread of communism so it joined the United States, including participating in SEATO alliance, sending expeditions to Korea and Vietnam, and offering the US to use its base.

Thailand ranks midway in the wealth spread in Southeast Asia as it is the fourth richest nation according to GDP per capita, after Singapore, Brunei, and Malaysia.

While the Asian financial crisis that followed in 1997 hit the Thai economy hard, the industrial sector continued to expand under widespread deregulation, as Thailand was mandated to adopt a range of structural adjustment reforms upon receiving funding from the IMF and World Bank.

These reforms implemented an agenda of increased privatisation and trade liberalisation in the country, and decreased federal subsidisation of public goods and utilities, agricultural price supports, and regulations on fair wages and labour conditions.

Scholars argue that the economic consequences and social costs of Thailand's labour reforms in the wake of the 1997 Asian financial crisis fell on individuals and families rather than the state.

[242] Informal labour in entertainment, nightlife, and the sex industry face additional vulnerabilities, including recruitment into circles of sexual exploitation and human trafficking.

Thai sculpture and painting, and the royal courts provided patronage, erecting temples and other religious shrines as acts of merit or to commemorate important events.

[318] Trai Phum Phra Ruang, written in 1345 by King Maha Thammaracha I, expounds Buddhist philosophy based on an extensive study with reference to over 30 sacred texts and could be considered the nation's first piece of research dissertation.

Sunthorn Phu is best known for his epic poem Phra Aphai Mani, a versified fantasy-adventure novel, a genre of Siamese literature known as nithan kham klon (Thai: นิทานคำกลอน).