Thailand's economy has always been very much based on decentralized free enterprise, and the laws are very similar to those in the free economies of the West. Sectors like telecommunications, energy and other infrastructure have been more like the European quasi-monopolies than American deregulation.
Thailand's infrastructure is excellent, especially the freeways, all over the country. Power, telephones and internet are all good. Thailand enjoys one of the best ratios of quality infrastructure to GNP per capita.
Thailand's economy was one of the fastest growing in the world in the 1980s and early 1990s (in terms of percent of GNP annually), but the 1997 Asia economic crash was the end to that. It is currently growing at approximately 4 to 5% per year.
Extreme poverty is low, and you don't see many hungry beggars on the street.
There are some key restrictions to foreigners, such as owning companies and property, as discussed in the "Working, Business" section of this website. Changes in the near future are unlikely. Nonetheless, there are various workarounds and these issues are not major barriers to most foreigners who have legitimate business to do in Thailand.
Despite Thailand's large size, the language and culture are fairly uniform, with no significant ethnic clashes. Civil unrest is practically nonexistent, except with some fringe Muslim separatists in the far south near the border with Malaysia (and of the Muslims in that region, onl a very small minority are separatist). Periodic problems along the border with Burma are usually related to suppression or control of the illicit drug trade. Inside Thailand, regional differences are quite minor.
Historically, Thailand was an Absolute Monarchy from the late 13th century until 1932, when it became a Constitutional Monarchy with an elected parliament. The monarchy has nonetheless played a leading role in society, though only occasionally and always briefly in politics, by the new tradition.
Between 1932 and 1992, Thailand's government alternated between democracy and dictatorships, sometimes with bloody clashes, the last of which in 1992 finally led to the end of any chance of another military takeover. A new "people's constitution" in 1997 significantly refined the checks and balances system and added some political stability.
Thailand's government civil service has been the most stabilizing force over the decades, with most of it operating more or less the same regardless of who was in power.