The Thai curry noodle soup especially associated with Northern Thailand is khao soi.
Northern Thai khao soi is a rich noodle soup built around curry paste, coconut milk, and meat, commonly chicken or beef. Its defining contrast is the combination of soft boiled egg noodles in the broth and crisp fried noodles scattered on top. Pickled mustard greens, shallots, lime, and chilli oil are typical accompaniments that balance the soup’s richness.
The dish is strongly associated with Chiang Mai and other parts of northern Thailand, but its history crosses modern borders. It is widely believed to have developed through Chin Haw Muslim traders from Yunnan, who travelled spice and caravan routes through Myanmar, Laos, and northern Thailand. It is related to Burmese ohn no khao swè.
Khao soi is often confused with Lao khao soi, which is a different noodle soup made with hand-sliced rice noodles and a tomato-based meat topping. The Thai version is also not simply a bowl of ordinary Thai curry poured over noodles.