Kirat Rai (also called Rai, Khambu Rai, Rai Barṇamālā and Kirat Khambu Rai) is a left-to-right abugida (a type of segmental writing system), based on the Sumhung Lipi of 1920s, used to write the Bantawa language in the Indian state of Sikkim.^[1] Kirat Rai is composed of 31 primary characters, including seven vowels (and seven related vowel diacritics), one of which (/a/) is inherent in all consonants, 31 consonants, a virama to cancel the inherent vowel, and a vowel carrier to be used in combination with the vowel diacritics for writing word-initial vowels.^[2]

Kirat Rai is part of the Brahmic family of scripts from India, Nepal, Tibet and Southeast Asia. Smriti Rai mentions that the Rai (Khambu) people, speakers of the Bantawa language, used to write with the Limbu (Sirijanga) script but created the Sumhung Lipi as the Limbu people started claiming the Limbu script.^[3] Both Sumhung Lipi and Limbu script have descended from the Old Kirat Lipi. Sumhung Lipi was created by Tika Ram Rai in the 1920s for writing religious book called Sumhung. In 1969 Kripasalyan Rai of Gyalshing district reintroduced^[4] and promoted Sumhung Lipi script as "Kripasalyan Lipi" through his book Rāī Akṣarko Barṇamālā.^[1]