In 2023, the annual population growth in Thailand amounted to -0.05 percent. Between 1961 and 2023, the figure dropped by 2.98 percentage points, though the decline followed an uneven course rather than a steady trajectory.

In 2020, the average age in Thailand is expected to reach 38.2 years, twenty years higher than in 1980, when it began to rise after a steady decrease in prior years. Previously, from 1950 to 1975, the average age hovered around 17 years. The increased average age corresponds with rising life expectancy globally, accelerating especially around the mid-twentieth century onward. In this century, the life expectancy in Thailand has increased by roughly 2.5 years since 2007, reaching 78.39 in 2017. The standard of living is increasing In Thailand, people ages 15 to 64 have consistently made up the majority of the population from 2007 to 2017. In this time, the older population grew increased by about three percent, while the younger population shrunk at roughly the same rate. This indicates that many people within the middle age category are reaching 65 or older, and that the birth rate is simultaneously declining. Birth rates are declining Every year, families are having fewer children in Thailand, with a fertility rate of less than 1.5 children per women of childbearing age in 2017. This is not necessarily a bad sign – it points towards increasing healthcare and living standards. Another indicator for this is the decreasing infant mortality in Thailand, meaning more of the children born each year survive. Lower infant mortality also contributes to the calculations of a higher life expectancy, and thus affects the country’s median age.

In 2023, the share of children in Thailand amounted to approximately 16.22 percent of the population. This was a slight decrease compared to the previous year, which amounted to 16.43 percent of the population in Thailand.