Published in 2012 in No. 7 of the Journal of the Research Institute for World Languages, Osaka University, this Japanese-language article by Sato Thuy Uyen (佐藤トゥイウェン), Shimizu Masaaki (清水政明), and Kondo Mika (近藤美佳) is titled “Quốc Phong Thi Tập Hợp Thái: A Poetry Collection in Chinese Characters, Chữ Nôm, and Quốc Ngữ in Nguyễn-Dynasty Vietnam” (「國風詩集合採」―阮朝ベトナムにおける漢字・字喃・国語字表記の詩集―). The article examines Quốc Phong Thi Tập Hợp Thái (國風詩集合採), an early twentieth-century Vietnamese compilation of popular verse and folk songs. It introduces the work’s textual structure and compilation history and considers it an important source for understanding Vietnamese vernacular language and literary culture during a period of major linguistic transition. The manuscript combines Chinese characters and chữ Nôm with handwritten romanized Vietnamese annotations, providing a valuable record of different writing systems in simultaneous use. Particular attention is given to the collection’s linguistic value. By comparing the Quốc Ngữ transcriptions preserved in the manuscript with modern Vietnamese pronunciation, the authors identify historical features associated with northern Vietnamese speech, including correspondences involving d/r/gi, tr/ch, and s/x. These features provide evidence for studying Vietnamese pronunciation in the early twentieth century. More broadly, the article demonstrates how Quốc Phong Thi Tập Hợp Thái documents a transitional moment in Vietnam’s writing culture, when Hán characters, chữ Nôm, and Quốc Ngữ coexisted. It therefore highlights the collection’s significance for research on Vietnamese folk poetry, historical linguistics, writing systems, and the transformation of textual practices in modern Vietnam.