That hat is only worn by Hmong women from a certain region in the country of Laos, it represents where they are from, I believe Xiengkhuang is where majority of Hmong women wear that hat, other clans and other regions elsewhere wear different type of clothes and hat as in their regions, that is history of their dress attire. You see this mainly in marriage wedding ceremonies, when the groom has taken the bride home, the bride and maid of honor (usually grooms sister or cousin) would wear the grooms family region clothes and hat to the brides family for the wedding so their family knows which region of Hmong the daughter is marrying into, once the wedding ceremony is finished, the bride and maid of honor return back to the grooms home with the brides family clothes attire. This is tradition and culture we preserve for Hmong so we know exactly where and what region they are from. To sum it up, the fashion represents where you are from. This purple hat is worn by most Hmong women because it is more dominant than the other smaller regions attire but understand that this represents Hmong Xieng, there is Hmoob Laug, Hmoob Npab (stripes on arms) and other ethnic regional attire. Then not to confuse anymore the other names like Hmong Green, White, blue, stripe etc. this represents language and clanship. Hmong is very diverse having segregated groups within each and older generations forget to teach younger generations this, I would have never knew if I never reached out and asked why their is different attire in hmong women clothes and not as much in hmong men clothes.