Pahawh Hmong is a script. It is used to write the Hmong language(s). Different scripts are quite the norm in Asian languages and it is for this reason that the Hmong take pride in the existence of "their" script. Pahawh Hmong was developed in 1959 and it has evolved in to three variants and this complicates things a lot.
At this time there is the opportunity for this script to be included in Unicode. It is a good time to do this; there is still someone alive who knew Mr Shong Lue Yang, and it takes some plane tickets and salary for the person researching and encoding the script into Unicode.
It is not just Wikipedia that requires Unicode for a script most applications do. Without it, you may write it with a fountain pen but effectively the language is not part of this modern world.
As it is, there is no money for the encoding of the Pahawh Hmong script...