The handbook delves into the linguistic features of Southeast Asian and South Asian endangered languages, providing detailed descriptions and analyses. Each chapter covers a range of topics, including linguistic properties, extralinguistic aspects, and issues related to preserving and promoting endangered languages. The book also includes an ethnolinguistic profile for each language, discussing its official status, state of endangerment, demography, and usage. It discusses the methodological issues related to collecting and analyzing linguistic data. Furthermore, the book describes the unique linguistic features of each language, covering phonology, morphology, morphosyntax, and other linguistic aspects. By doing so, the book highlights how new linguistic features and findings can reflect on the community. Given the context of UNESCO's declaration of the 'International Decade of Indigenous Languages 2022-2032', this book offers valuable insights for students, researchers, policymakers, government agencies, educators, and linguists. It is an informative volume for scholars working on various endangered languages worldwide.