Ayutthaya Kingdom
Transition to a hinterland state

The Ayutthaya Kingdom shifted from a maritime state to more of a hinterland state during the 15th and 16th centuries. Its absorption of the Northern Cities and the shifting of trade power to the inland trade routes with China facilitated this change of policy. The reign of King Borommatrailokkanat was the peak of this merger between the basin and the Northern Cities, being the scion of generations of intermarriage between the two.

Even though Trailokkanat symbolized the merger between North and South, the Lan Na Kingdom, a state North of Ayutthaya (modern-day Northern Thailand), contested Ayutthaya's growing influence over the Northern Cities. The Ayutthaya-Lan Na War was fought over the Upper Chao Phraya valley for control of the Northern Cities. Whether he preferred the Northern Cities to Ayutthaya or the necessity to have a capital closer to the war, Trailokkanat moved his capital to Phitsanulok. Lan Na suffered setbacks and Trailokkanat eventually sued for peace in 1475.

Ayutthaya's sphere of influence down the peninsula was contested by the Malacca Sultanate. Ayutthaya launched several abortive conquests against Malacca which was diplomatically and economically fortified by the military support of Ming China. In the early-15th century the Ming admiral Zheng He established a base of operation in the port city, making it a strategic position the Chinese could not afford to lose to the Siamese. Under this protection, Malacca flourished, becoming one of Ayutthaya's great foes until the capture of Malacca by the Portuguese. Ayutthaya's attention to the portage routes across the upper peninsula meant that it did not send a military expedition to the lower peninsula and the Malay States throughout the 16th century.
detectable_content:postscript, startend:quotation