In Tibetan Buddhism the mantra is pronounced differently. There it’s Om ah hung benza guru pema siddhi hung . The difference arises solely because Tibetan and Sanskrit are from different language groups, and the sounds of Sanskrit are not easily pronounced by Tibetans. This doesn’t mean that the Tibetan form is wrong; Om ah hung benza guru pema... See more

Oṃ Āḥ Hūṃ Vajra Guru Padma Siddhi Hūṃ