Vietnamese, for example, all know who is Mulan but very few can name a Thai princess. Indonesians do not care too much about Filipino culture and Filipino princess will just excite them as much as another white blonde Disney princess. read more
I don't think lack of exposure to the culture is the reason, rather it is because a SEA princess does not have a sufficiently large target market. Cinderella for example appeals to Europeans because she is a well known person in European tales. read more