"Om Ah Hum Vajra Guru Padame Siddhi Hum"
Also there is 7 Line prayer for the Padama Shambhava called "The vajra Guru seven-line Prayer".
Good News!! This 7 line prayer is Now available at Ani choying Drolma's latest Album INNER PEACE-2.
please read more at The Vajra Seven-Line Prayer to Guru Rimpoche
Guru Padma Sambhava Seven Line Prayer in Tibetan Language