I followed the "method" of "Suma Ching Hai" for a while, three or four years ago, before leaving because I saw no point in continuing to waste time on a method that seemed fictional. "Light and sound" simply did not occur during any of my meditations!
There is no evidence of a mantra in this group because nothing is written. The first few times you meditate, you are instructed to repeat "Suma Ching Hai" internally for 30 minutes a day. You are advised to give up meat, fish and eggs and all intoxicants. After a few weeks/months, you are invited to be "initiated". You are, they hope, fully vegetarian by this time.
You are simply told that the "Five Names" (of God) that you are to repeat internally when meditating (2 1/2 hours a day). You are also told how to meditate on "light and sound", by concentrating on the "third eye," which is supposedly in the region of the pineal gland, between the eyebrows, and also by blocking your ears and listening to the celestial sounds within. These can be the sound of bells or other "heavenly music". I would not know: I heard nothing and "saw" nothing. You are told of "brilliant light", although sharing experiences is discouraged, because not everyone is the same. You are also asked to cover yourself with a sheet or blanket, so no one can see you even when meditating in a group of fellow "disciples." [These techniques of meditation appear to be a kind of self-hypnosis to achieve a trance state.]
The "Five Names" are YO NI RAN YAN, OM GAR, RA RAN GAR, SO HAM, SATT NAM. I have no idea how to spell these, of course, since it is all passed on orally. You are told never to repeat these "names" aloud and, of course, never to tell anyone else about them. Ooops! Does that mean I am now officially a "sinner" in the eyes of Ching Hai devotees?
There's not much more to tell, except that 2 1/2 hours was too much for me. I have four children and work as well. Also, the books and other paraphernalia were over-priced. The books and tapes could be borrowed if you liked, and once you were an official follower, you had an ID card, with your photo on. This was to be carried with you, although no one ever asked me for it. You need never give any money at all, if you did not want to. There was no pressure at all in my Sussex group in England and everyone seemed very pleasant.
I never came to any harm from Ching Hai or her following. Meditation made me calmer, but sitting on your bum thinking of very little is bound to calm you down anyway!
I did once see Ching Hai, in London. She was a small woman, dressed in very plain clothes and with an incredible amount of charisma. She talked for a while and then invited questions. I asked one and was impressed by her direct manner and down-to-earth, practical reply. She had a way of looking in your eyes, as if she knew you completely. I cannot describe it more exactly than that, but there was definitely some power there, despite her slight physical frame.