Most of the area from foothill up to 1,200 meters above mean sea level is trespass by hill tribe for their cultivation and forest turn to the abandon area or grassland. The forest, that higher than 1,200 meters above mean sea level, is still well-preserved area in the south of national park. The vegetation of Phu Hin Rong Kla National Park includes deciduous dipterocarp forest, mixed deciduous forest, dry evergreen forest, lower montane rainforest and lower montane scrub (Soil and forest resources part National Resource Conservation Office, 1997).
1. Dry dipterocarp forest can be found on mountain slopes at elevation of 600 meters. Only small tree and frutescent plant are found because trees were cut off. Characteristic trees include: Dipterocarpus tuberculatus Roxb., D. obtusifolius Teijsm. ex Miq., Shorea obtusa Wall. ex Blume, S. siamensis Miq., Pterocarpus macrocarpus Kurz, Albizia odoratissima (L. f.) Benth., Phyllanthus emblica L., Fernandoa adenophylla (Wall. ex G. Don) Steenis etc.
2. Mixed deciduous forest can be found in groups alternate with dry dipterocarp forest that appears in narrow strip at dry evergreen forest boundary and the soil fertility is richer than dry dipterocarp forest. Characteristic trees include: Pterocarpus macrocarpus Kurz, Xylia xylocarpa var. kerrii (Craib & Hutch.) I.C. Nielsen, Millettia brandisiana Kurz, M. leucantha Kurz var. buteoides (Gagnep.) P.K. Loc, Bauhinia malabarica Roxb., Careya sphaerica Roxb., Lagerstroemia macrocarpa Wall., Gardenia coronaria Buch.-Ham. Cratoxylum formosum (Jacq.) Dyer etc.
3. Dry evergreen forest was appeared in large area at 300-800 meters but at present it was completely cleared. The trees that still remain in deforestation area are Lagerstroemia calyculata Kurz, Irvingia malayana Oliv. ex A.W. Benn., Anogeissus acuminata (Roxb. ex DC.) Guill. & Perr. var. lanceolata C.B. Clarke, Mangifera caloneura Kurz, Anisoptera costata Korth., Stereospermum fimbriatum (Wall. ex G. Don) A. DC., Alstonia scholaris (L.) R.Br., Xerospermum noronhianum (Blume) Blume etc.
4. Lower montane rainforest can be found in the south of Phu Hin Rong Kla National Park at 1,200 meters above mean sea level. The crown covers dense and continuous. Characteristic trees include: Calophyllum polyanthum Wall. ex Choisy, Knema globularia (Lam.) Warb., Cinnamomum iners Reinw. ex Blume, C. tamala (Hamilton) Nees & Eberm. Acer calcaratum Gagnep. and members of Fagaceae such as Castanopsis acuminatissima (Blume) A. DC., C. brevispinula Hickel & A. Camus, C. echidnocarpa A. DC., C. crassifolia Hickel & A. Camus, Lithocarpus polystachyus (A. DC.) Rehder, Quercus aliena Blume, Q. kingiana Craib. In forest fire disturbance area, Pinus kesiya Royle ex Gordon and P. merkusii Jungh. & de Vriese are usually found with Fagaceae members.
5. Lower montane scrub can be found in rocky open space. It is consist of small tree or shrub in rock crevice, epiphytic plant and parasitic plant. Characteristic trees include: Rhododendron lyi H. Lév., Rhamnus crenata Siebold & Zucc., Melastoma malabathricum L. subsp. normale (D. Don) F.K. Mey., Hedychium ellipticum Buch.-Ham. ex Sm. Fagraea ceilanica Thunb. etc.