It's the Tibetan syllable TAM, the seed syllable of the female buddha Tara (sanskrit) or Dölma (tibetan), which translates as Liberatress. As it is white here, it stands for the White Tara, which especially gives the blessings for a long life:
Manjusri, bodhisattva of wisdom, is one of the most important iconic figures in Mahayana art and literature. He represents the wisdom of prajna, which is not confined by knowledge or concepts. His Sanskrit name means "He Who Is Noble and Gentle.
Parnashavari the Forest Goddess: Healer of Contagious Diseases invoked at Tibetan Tantric religious gatherings. Associated with the Shavari tribe of ancient India, she wears a garland and skirt of thatched leaves.