Administrative centralization of Siam attributed to efforts of King Trailokanat (r. 1448–88); but most of institutionalized form of government probably resulted from reign of King Naresuen the Great (r. 1590–1605). Under this king, Siam regained its independence from Burma and emerged as most powerful kingdom in mainland Southeast Asia.
Development of overseas trade can be dated as early as 1368. By the early modern period, Siam was a major source for sappanwood and pepper in the Chinese trading network.
Siamese adopted Hinduism along with Theravada Buddhism. Hindu concept of divine kingship, and accompanying rituals, provided important sources of legitimation. But in Siamese society, the claim to divinity operated without the internal checks characteristic of India, for Brahmans had little influence at the court. This may explain the pronounced aspect of absolutism in Siam. Yet Buddhism was dominant in the cultural system that emerged in the early modern period, particularly in providing signs of legitimation (and delegitimation in the face of popular unrest) for rulers. Royal interaction with sangha (groups of monks) provided especially important occasions for public statements of rulers' support of Buddhist precepts; nevertheless, Thai rulers closely controlled the sangha through cultural patronage (their support ranged from sponsorship of architecture and sculpture to public processions).
New fortification style was introduced around the Siamese capital. King Maha Thammarcha (r. 1569–90) also purchased large supplies of foreign cannon. Consequently, by the time Naresuen the Great launched campaign to consolidate Siam, the Siamese royal army was well equipped and trained in the use of firearms.
King Naresuen the Great regained independence and utilized political, economic, and military forces to transform fragmented kingdom into relatively centralized state.
Portuguese trading stations were established in the 16th century, and around the beginning of the 17th century large numbers of Japanese were active in Siam in war and trade.
By a commercial treaty, the Dutch gained a monopoly of Siamese foreign trade, which was, however, thwarted by French intrigue; a French embassy and military expedition (1685) in turn failed to secure the acceptance of Christianity and French influence and led to
A popular revolt that began a period of prolonged civil war. Prompted in part by reaction against Narai's openness, it became anti-European. European trade languished, but Chinese and Muslim trade continued at a high level to take up the slack.
