One of the oldest and most important monumental structures in Thailand is the Prang. It arrived in Thailand from India via Angkor Wat and first found favour in Khmer temples of the Northeast. As a Khmer structure such as those at the Bayon its upper portion was decorated with the four faces of Brahma facing the four cardinal directions. Adopted by the Buddhists, it was altered to contain niches for images as can be seen at Wat Arun, Wat Po and Wat Phra Kaew. It originally held relics of Buddha but in later times was used to hold the ashes and relics of kings, holy men, and important personages.

Some see the prang as a closed lotus bud, others, as a modified form of Siva's lingam. In whatever form, it is a powerful symbol of potency which was appreciated by Ayutthayan builders who made it the centerpiece of their wats. The prang resembles an ear of corn or a cucumber stood on end and pointing at the sky. Like the Hindu prang, the Buddhist prang has six tiers on its upper portion, the seventh, the topmost, being a depiction of Nibanna or Nirvana, the most exalted heaven. The entire structure is crowned by a 'nophasun' equivalent to the Hindu vajra or thunderbolt. Around the base of the lowest tier is a ring of demon guardians who protect the deities from the inhabitants of earth and hell. Those of Wat Arun are good examples of this type of decoration. Prangs were also used to crown royal buildings such as the royal pantheon. Here, their presence symbolises that the building is the abode of living deities, a belief which stems from the deva-raja (god-king) concept adopted during the Ayutthayan period.

The chedi, one of the most beautiful of all Thai architectural forms, was also derived from India via Sri Lanka. It originally held relics of Buddha and later his scriptures. By the Ayutthayan period it had come to mark the site of the cremation of a well-known king or the abbot of a Wat. Today, anyone with sufficient money can build one as a receptacle for his or her ashes. Stouter versions of the chedi were originally called stupas but today the terms are used interchangeably with "chedi" given almost exclusive preference over "stupa" in Thai terminology.