It is not he, but rather Niam Luang Mey. The amulets are of her, and not Luang Phor. I don't know how many versions there are, but the one I heard goes like this:
A female monk, Niam Luang Mey, appears out of nowhere and request an audience with Luang Phor. She tells him that she is Hmong and that her people will be pouring in into Thailand soon. Niam Luang Mey tells Luang Phor that when she dies and her body turns into stone then Luang Phor must help her people. If it doesn't, then Luang Phor does not have to do anything.
She dies and her body, including the tree that her casket is made from, turns to stone and so Luang Phor takes in some Hmong refugees. Luang Phor tells them the story and so Hmong people wear pieces of Niam Luang Mey and the tree as talismans.