Garcinia nuntasaenii Ngerns. & Suddee (Clusiaceae), a new species from north-eastern Thailand, is described and illustrated. It is a dioecious shrub in dry evergreen forest at ca 150–220 m altitude.

GarciniasectionXanthochymus(Clusiaceae) is revised for Thailand with four native species,i.e.,G. dulcis,G. nervosa,G. prainiana, andG. xanthochymus. All species are described with updated morphological descriptions, illustrations, and an identification key, together with notes on distributions, distribution maps, habitats and ecology, phenology, conservation assessments, etymology, vernacular names, uses, and specimens examined. Four taxa,G. andamanica,G. andamanicavar.pubescens,G. cambodgiensisandG. vilersiana, are synonymized underG. dulcis, and two taxa,G. nervosavar.pubescensandG. spectabilis, are newly synonymized underG. nervosa. Nine names are lectotypified:G. dulcisand its associated synonyms (G. cambodgiensisandG. vilersiana),G. nervosaand its associated synonyms (G. andersonii,G. nervosavar.pubescens, andG. spectabilis),G. prainiana, andG. xanthochymus. All species have a conservation assessment of Least Concern (LC). The fruits of all species are edible and have a sour or sweet-sour taste.

A revision of the genus Garcinia has recently been undertaken by the author as part of the Flora of Thailand. Herbarium specimens deposited in several herbaria, and those included in the digital herbarium databases, were examined by consulting taxonomic literature. In this study, the three names in Garcinia section Brindonia are lectotypified as G. gracilis, G. lanceifolia and G. planchonii. A new synonym for G. pedunculata, namely G. planchonii, is proposed. Detailed descriptions, recognitions and illustrations of three species in Garcinia (G. atroviridis, G. lanceifolia and G. pedunculata) are presented, along with information on distributions, specimens examined, habitats and ecology, IUCN conservation status, phenology, etymology, vernacular names and uses. The fruits, the young shoots and leaves, and the flowers of these three species are edible and have a sour taste. These species are often cultivated for their fruits.

Garcinia section Garcinia (Clusiaceae) is revised for Thailand with three species and one variety, i.e., two native species: G. celebica and G. exigua, and one cultivated species: G. mangostana var. mangostana. Detailed morphological descriptions, illustrations, and an identification key to the species are presented, along with notes on distributions, habitats and ecology, phenology, conservation assessments, etymology, vernacular names, uses, and specimens examined. The section is recognized by its terminal inflorescences of simple cymes, or sometimes a solitary flower; flowers with 4 sepals and 4 petals; male flowers often with a pistillode, and stamens united into a single 4-lobed or 4-angled bundle, and with 2-thecous anthers; usually multilocular ovaries and stigmas with distinct or weak lobes and smooth or rough; and fruits with a smooth surface. Three associated synonyms of G. celebica: G. ferrea, G. basacensis, and G. hombroniana, are lectotypified here in a second-step. In Thailand, Garcinia celebica is found in a very wide variety of habitats, at elevations of 0–1,500 m amsl., and is known to be naturally distributed in all floristic regions. G. exigua is found in dry evergreen forest on limestone hills and in littoral dry evergreen forest on limestone hills, at elevations of 50–100 m amsl. in Krabi Province, the peninsular region. G. mangostana var. mangostana is found only in cultivation. Garcinia exigua has a conservation status of Vulnerable [VU B2ab(iii)] and the other two species have a conservation status of Least Concern [LC]. The fleshy pulp surrounding the seeds of two species, G. celebica and G. mangostana var. mangostana is edible and has a sweet-sour taste.

Garcinia exigua (Clusiaceae), previously known from Borneo [Malaysia (Sarawak) and Brunei], is reported as a new record from dry evergreen forest on limestone hill in Krabi Province, Peninsular Thailand. A detailed morphological description, illustrations and a distribution map of the species are provided, along with information on distribution, specimens examined, habitat, conservation status, phenology, etymology and vernacular name.