During Rama II's reign, the kingdom saw a cultural renaissance after the massive wars that plagued his predecessor's reign; particularly in the fields of arts and literature. Poets employed by Rama II included Sunthorn Phu the drunken writer (Phra Aphai Mani) and Narin Dhibet (Nirat Narin). Foreign relations were initially dominated by relations with the neighbouring states, while those with European colonial powers started to enter in the background. In Cambodia and Laos, Vietnam gained the supremacy, a fact which Rama II initially accepted. When a rebellion broke out in Vietnam under Rama III in 1833–34, he tried to subdue the Vietnamese militarily, but this led to a costly defeat for the Siamese troops. In the 1840s, however, the Khmer themselves succeeded in expelling the Vietnamese, which subsequently led to the greater influence of Siam in Cambodia. At the same time, Siam kept sending tribute to Qing China. Under Rama II and Rama III, culture, dance, poetry and above all the theatre reached a climax. The temple Wat Pho was built by Rama III, known as the first university of the country.

The reign of Rama III. was finally marked by a division of the aristocracy with regard to foreign policy. A small group of advocates of the takeover of Western technologies and other achievements were opposed by conservative circles, which proposed a stronger isolation instead. Since the kings Rama II and Rama III, the conservative-religious circles largely stuck with their isolationist tendency. The death of Rama III in 1851 also signified the end of the old traditional Siamese monarchy: there were already clear signs of profound changes, which were implemented by the two successors of the king.