About Thothori Nyantsen

Lha Thothori gNyan bTsan was the 28th King of Tibet according to the Tibetan legendary tradition. Buddhism came to Tibet during the reign of King Thothori Nyantsen (245-364 A.D.,) Lha "divine, pertaining to the gods of the sky" is an honorary title and not a part of his proper name.
Lama Teacher Gotsangpa Gonpo Dorje

The most prominent Tibetan kings

The Tibetan kingdom was centered on the Tibetan Plateau, formed as a result of imperial expansion under the Yarlung dynasty heralded by its 33rd king, Songtsen Gampo, in the 7th century. The empire further expanded under the 38th king, Trisong Detsen. The 821–823 treaty concluded between the Tibetan Empire and the Tang dynasty delineated the former as being in possession of an area larger than the Tibetan Plateau, stretching east to Chang'an, west beyond .