The Emerald Buddha is the object on which Thai royal legitimacy rests, and Laos regards it as stolen.
The chapel
Wat Phra Kaew sits inside the Grand Palace and is a chapel of the crown, not a monastery. No monks live there. Monks are brought in from other temples to perform rites and then leave.
That distinction matters. This is not a religious institution that the monarchy patronises; it is an instrument of the monarchy that happens to be religious.
The image
Sixty-six centimetres tall, of jade or jasper, not emerald, which describes its colour. It sits high on a gilded altar, deliberately far from viewers.
Tradition places its making in India in the first century BCE. Art historians date it to fifteenth-century northern Thailand.
The itinerary
Its documented travels begin in 1434, when lightning struck a stupa at Chiang Rai and revealed it, reportedly under plaster, which had disguised it.
Then: Lampang, then Chiang Mai, then in 1552 to Luang Prabang with King Setthathirath, and later to Vientiane. It remained in Laos for more than two centuries.
In 1779 Siamese forces under General Chakri, later Rama I, took Vientiane and carried the image back. Rama I enshrined it in his new capital in the 1780s.
The claim from Laos
Laos regards the seizure as looting, and the image's absence is still felt there. Its return has been raised periodically and never conceded.
This is worth stating because of what it implies about the object's function. The Emerald Buddha works as the palladium of the Thai state because it was removed from another kingdom. A palladium that could be acquired without conquest would not demonstrate anything. The legitimacy it confers on one monarchy is the same event that constitutes a grievance for a neighbouring one.
The robes
The king personally changes the image's gold robes three times a year, at the turn of the hot, rainy and cool seasons. There are three sets and they are not interchangeable.
The rite is performed by the monarch and by nobody else. When the king has been unable to perform it, it has been done by the crown prince or a regent acting expressly on his behalf, the substitution being noted rather than passed over.
It is one of the few surviving royal rituals anywhere in which the sovereign performs a physical act of service to an object, in person, on a fixed schedule, as a condition of the relationship the state depends on.