The Hall of Opium, known in Thai as Ho Fin, in Chiang Rai, near the Golden Triangle, an infamous area that got its name from the cultivation of opium.

The hall is a museum and a royal project of the Mae Fah Luang Foundation under the auspices of the Queen Mother (fig.), Princess Sri Nagarindra.

The permanent exhibition aims to educate about opium and portrays every aspect of the opium story, from its origin and history, including the Opium War, the effects of the drug, to the battle against it.

The museum includes a 137-meter-long tunnel with bas-reliefs, as well as displays of smoking dens, statues of historical figures, tools and science used for the development of the drug, and its overall effects on society.