He consulted with William A. Smalley, a missionary studying the Khmu language in Luang Prabang Province at the time.
Concurrently, Yves Bertrais, a Roman Catholic missionary in Kiu Katiam, Luang Prabang, was undertaking a similar project with Chong Yeng Yang and Chue Her Thao.
Much as with Tosk for Albanian, White Hmong was arbitrarily chosen to be the "standard" variant.
RPA indicates tone by letters written at the end of a syllable,[4] similarly to Gwoyeu Romatzyh or Zhuang, rather than with diacritics like those used in the Vietnamese alphabet or Pinyin.
Unlike Vietnamese and Chinese, all Hmong syllables end in a vowel, which means that using consonant letters to indicate tone will be neither confusing nor ambiguous.