Hmong(Hmoob) comes from the Miao language that was spoken by the Hmong in Thailand, Laos, Vietnam, and China. It has been suggested that there are over 4.5 million speakers of this Hmong language.
The two major dialects that are used by Hmong-Americans are the Green(Moob Leeg) and White(Hmoob Dawb). Green and White hmong languages are mutually intelligible – they understand each other fine.
You should know right off that the Hmong language is definitely a tone-based language and therefore words sound very similar to each other. It is not uncommon for non-Hmong speaking people to think the words sound the same while in fact they have completely opposite meanings. There is about 8 different tones that are used in the Hmong language. Many linguists say that if you can master these tones you will be speaking Hmong in fluently soon after.