The genus Terniopsis consists of plants that have not been thoroughly studied, with many species remaining taxonomically unresolved. In this study, Terniopsis chanthaburiensis is reported as a new record of China based on morphological traits. Then, we assembled and annotated its chloroplast genome based on genome skimming data. A maximum-likelihood tree constructed based on the matK and ITS genes showed that jflcz20230309 clustered with T. chanthaburiensis (LC625800, LC384161, and LC625815, LC625816). This validates our morphological identification. Furthermore, the plastome of T. chanthaburiensis has been sequenced, revealing a typical quadripartite structure with a length of 130,529 bp. It contains 105 unique genes, including 73 protein-coding genes, 28 tRNAs, and 4 rRNAs. Phylogenetic analysis based on the plastid genome reveals that T. chanthaburiensis (collection number: jflcz20230309, GPS: 108°47′37.2012″E, 18°41′48.9624″N, collection date: 9 Mar. 2023) forms a distinct clade sister to T. yongtaiensis and T. heterostaminata, with high support values (PP = 1.00, BS = 100). The discovery of this river-weed could lay the foundation for investigating their biogeographical patterns and species evolution.