An account of Korthalsia (Arecaceae) rattans and their uses in Thailand.

Four species of Korthalsia are found in Thailand: K. flagellaris, K. laciniosa, K. rigida, and K. scortechinii. We present the comparative vegetative morphology, a key to the species, distribution, ecology, preliminary conservation assessments, utilization, and specimens examined. Korthalsia flagellaris is lectotypified here in a second-step. Three Thai Korthalsia species are confined to the peninsular region: K. flagellaris, K. scortechinii and K. rigida. The first, K. flagellaris, is known only from Narathiwat province and is restricted to peat swamp forests. The second, K. scortechinii, is myrmecophilous and found only in Narathiwat in lowland tropical evergreen rainforests. The third, K. rigida has a wider distribution and is known from Ranong, Trang and Narathiwat provinces in lowland tropical evergreen rainforests. Lastly, Korthalsia laciniosa is the most widespread species of the genus in both the south-eastern and peninsular regions of Thailand in lowland tropical evergreen rainforests. All Thai Korthalsia species are currently assessed as Least Concern (LC) under the IUCN conservation status. In Thailand, Korthalsia is used for traditional tools, furniture components, and fishery equipment. Its stems are valued in local crafts, while the young shoots are occasionally consumed as food.