Alocasia sakonakhonensis Chatan & Promprom (Araceae), a new species from northeastern Thailand, is described and illustrated. It is clearly different from other previously known species by leaves, spathe, ovary, sterile interstice, synandria, and appendix. Color illustrations, and a distribution map are provided, as well as comparative morphological characters about its similar species. The preliminary conservation status assessment of the new species was presented.

Amorphophallus sakonnakhonensis Chatan & Promprom, a new species from northeastern Thailand, is described and illustrated. The new species is most similar to A. harmandii Engl. & Gehrm. and A. linearis Gagnep., but it is distinguished by the combination of characters as follows: clear differences with A. harmandii are shorter style; disc-like, slightly smooth surface, concave centre, ca. 0.2 × 0.1 mm stigma; slightly cylindrical, slightly narrower upper part of staminate flower zone; slightly cylindrical to elongate-fusiform, erect or slightly erect, creamy white appendix. The clearly distinct morphology with A. linearis are disc-like, slightly smooth surface, concave centre, ca. 0.2 × 0.1 mm stigma; elliptic or obovate leaflet; 1–3 cm long, creamy white appendix. The preliminary conservation status was assessed, and the distinct characteristics of similar species were discussed.

Colocasia sookchaloemiae (Araceae) is described from Phu Pha Yol National Park (northeastern Thailand). It is morphologically similar to C. fallax , from which it differs in having seasonal dormancy (vs. evergreen), broader and non-glaucous laminae (vs. narrower and slightly glaucous beneath), a speckled green ovary (vs. mostly green), a convex stigma with a depressed center (vs. 3-lobed), a sparsely hairy sterile interstice (vs. glabrous), and a thicker stipitate appendix (vs. slender, often sessile, or shortly stipitate). A comparative study of living plants, cultivated specimens, and herbarium material (including types) supports its recognition as a distinct species. The new taxon grows on rocky cliffs in dry dipterocarp and mixed deciduous forests at 350–400 m a.s.l., and it is currently known from Mukdahan and Sakon Nakhon provinces. A preliminary IUCN assessment indicates that the species is Data Deficient (DD).

A new subspecies, Ardisia crenata Sims subsp. mukdahanensis Chatan & Promprom (Primulaceae), is described from Mukdahan Province, Thailand. This discovery was made during field studies conducted from 2021 to 2023, during which the authors collected and analysed specimens, comparing them with relevant taxonomic literature and herbarium collections. A. crenata subsp. mukdahanensis is distinct from its closest relative, A. crenata subsp. crassinervosa by a combination of morphological traits, such as moderately dense minute hairs on young shoots, abaxial side of young lamina and calyx, peduncles and pedicels; larger flowers (7.0–7.5 mm) that are pure white or pinkish; larger fruits (7–8 mm) and absence of glandular punctation in organs such as lamina, calyx, corolla, anther and fruit. This new subspecies grows in slightly dense dry evergreen forests or open areas near streams and is preliminarily assigned to the Data Deficient (DD) category according to IUCN guidelines.

Amorphophallus coudercii is reported as a new record from Nakhon Phanom Province, North-Eastern Thailand. The species is characterized by having a long tuber, a male floral zone contiguous to the female zone, the absence of an appendix, and the presence of warts on the adaxial side near the base of the spathe. Detailed descriptions based on recently collected plant materials, as well as notes on the distribution and ecology, and photographs are presented.

A new liana species of the subfamily Caesalpinioideae (Leguminosae), namely Bauhinia nakhonphanomensis, collected from the Phulangkha National Park, Nakhon Pran