Chatt, Chatra

In Brahmanic, Vishnuite and Sivaite traditions, canopy, parasol part of the gods' royal emblems (mahārājopacāra) of gods, especially of Shiva. Ancient symbol of kingship and sanctity, notably for the chakravarti, 'universal ruler'.
In Buddhism, the sunshade beneath which Gautama sat. In Jainism and certain forms of Buddhism, the chatra is one of the ashtamangala, the eight holy symbols of enlightened sages and buddhas.
In Southeast Asia, the tiered parasol have 3, 7, 8, or 9 tiers. In Thailand, the chatra (also called brah klat) form has been strictly codified: five tiers for the prince, seven for the crown prince or the viceroy, and nine for a sovereign and crowned king. The Nine-Tiered Great White Umbrella of State (นพปฎลมหาเศวตฉัตร) is revered as the most sacred regalia of Thai sovereigns, and Coronation Day (วันฉัตรมงคล:, lit. 'the day of the blessing of the umbrella', was a public holiday until 2018.
In Cambodia, the royal umbrellas are made of various tiers, while processional chatras are usually 5-tiered, and large single-tiered umbrellas - as seen on Angkor bas-reliefs - are used as sunshade. There is a tradition (so far unverified) that when the Siamese kings 'allowed' the coronation of King Norodom of Cambodia in 1860, they explicitely forbade the use of 9-tiered chatras by the Cambodian soveregns. Monks going around for alms usually hold simple umbrellas, and in modern Khmer chatr refers to the common umbrella.
Stylized multi-tiered umbrellas such as banana leaf or paper decorations, food ornementations, architectural pyres, express a cosmological symbol shared by 'waterfront' ethno-cultures existing 'Japan to Bali to mainland Southeast Asia', according to Thai architect Sumet Jumsai.

Source

Bucknell's Sanskrit Manual 請先打入-再加上語尾
H.G. Quaritch Wales, Siamese State Ceremonies: Their History and Function, London, Bernard Quaritch, 1931.
Sumet Jumsai, NAGA: Cultural Origins in Siam and the West Pacific, Oxford University Press, 1988.