The population of Thailand is now 61.5 million, about 10 million of whom live in the capital city of Bangkok. Thais form the majority, though the area has historically been a migratory crossroads, and thus strains of  Mon, Khmer, Burmese, Lao, Malay, Indian and most strongly, Chinese stock produce a degree of ethnic diversity. Integration is such, however, that culturally and socially there is enormous unity. 

The largest ethnic minority is the Chinese and other ethnic groups include Malays, Cambodians, Vietnamese, and Indians. 

According to estimates of United Nations Population Information Network, the population of Thailand would be about 74 million in the year 2050. 

Approximately 68% of the population lives in rural areas and the majority are farmers with incomes reliant upon subsistence agriculture. Rapid change has had a disruptive effect on social structures. Urban migration to Bangkok, the capital city, has led to serious problems of congestion, land shortage, and water and air pollution. Although a period of fast economic and social transformation has improved the quality of life, there is now evidence that the income inequalities both within and between regions and between rich and poor groups are widening. The replacement of the extended family by the nuclear family has weakened the sense of community and traditional forms of co- operation and safety nets, increasing the vulnerability of disadvantaged groups. Drug addiction and crime are on the increase.

Thailand (previously Siam) has always been a multi-ethnic, multi-confessional society. More than 85% speak a variant of Thai and share a common culture, though there is a strong sense of regional identity and pride in many areas of Thailand. Roughly one-third of the population is in central Thailand, including Bangkok; one-third in the northeast, with significant Lao and Khmer heritage; 20% in the north; and 15% in the south. Ethnic Malay Muslims comprise a majority in the three southernmost provinces.

Central Thai is the language taught in schools and used in government. Lao, as well as “Isaan dialect”, is spoken widely in northeastern Thailand; “Gam Muang” or northern dialect is spoken in the north; and a southern Thai dialect in the mid-south. Several other Tai dialects are spoken among smaller groups, such as the Shan (Tai Yai), Lue, and Phutai.

Up to 12% of Thai are of significant Chinese heritage, but the Sino-Thai community is the best integrated in Southeast Asia. Other groups include the Khmer in border provinces with Cambodia; the Mon, who are substantially assimilated with the Thai; and the Vietnamese. Smaller mountain-dwelling tribes, such as the Hmong, Mein, and the Karen, number about 788,024.

The population is mostly rural, concentrated in the rice-growing areas of the central, northeastern, and northern regions. However, as Thailand continues to industrialize, its urban population--31.6% of total population, principally in the Bangkok area--is growing.

Thailand's highly successful government-sponsored family planning program has resulted in a dramatic decline in population growth from 3.1% in 1960 to less than 1% today. Life expectancy also has risen, a positive reflection of Thailand's public health efforts. Thailand’s model intervention programs in the 1990s also averted what could have been a major AIDS epidemic. Even so, today, approximately 1.4% of the adult population lives with HIV/AIDS.

The constitution mandates at least 12 years of free education; however, only 9 years are compulsory. In early 2009, the government put into effect a program to provide 15 years of free education (3 years in preschool and grades 1-12). Education accounts for approximately 18.0% of total government expenditures.