This letter belongs to the Thai high consonant class
A silent, high-class ห "leads" low-class nasal stops (ง(ngɔɔ), ญ(yɔɔ), น(nɔɔ) and ม(mɔɔ)) and non-plosives (ว(wɔɔ), ย(yɔɔ), ร(rɔɔ) and ล(lɔɔ)), which have no corresponding high-class phonetic match, into the tone properties of a high-class consonant. In polysyllabic words, an initial mid- or high-class consonant with an implicit vowel similarly "leads" these same low-class consonants into the higher class tone rules, with the tone marker borne by the low-class consonant.