No, these funny hats are not just part of a dance costume. There are actually something that is worn on a day to day basis. 云南十八怪。斗笠反着戴. In the book 18 Oddities of Yunnan. This hat is listed as one of the “oddities” and it is actually an integral part of the traditional costume belong to the “huayao” Dai people (so called because they wear a patterned, multi-colour belt around their waists). With no hollow in the hat itself, each hat must come with a “sock”. There is no explanation for why these people wear their hats this way. However, the Dai people are famous for their beauty contests and an emphasis on appearances may have led to this practice.
The huayao Dai are ethically identical to the Dai people who reside in Xishuangbanna. Their home lies in Central Yunnan around Xinping and Yuanjiang. There are also pockets of them in neighbouring Sichuan.
One thing to note, though. The actual huayao Dai costume does not leave the woman’s waist so exposed.