Sai Yohk (ไทรโยค)

Thai. ‘Swaying Banyan’ or ‘Swinging Strangler Fig’. Name of a protected natural area in western Thailand, Kanchanaburi Province, situated along the Kwae Noi River (fig.) near the Thai–Myanmar border. The name is commonly understood to describe large banyan or strangler fig trees growing along cliffs or riverbanks, with aerial roots and branches hanging down and swaying above the water—an image that fits the landscape around the waterfall and river. The area has National Park status and encompasses approximately 312,500 rai, equivalent to about 500 square kilometres, and is characterised by a predominantly mountainous landscape formed by complex ridgelines and steep slopes, with elevations ranging from around 100 metres to a maximum of approximately 1,132 metres above mean sea level at the Ro Rae (เราะแระ) mountain range. Flat or gently sloping terrain is limited and occurs mainly along riverbanks and valley floors, reflecting the park’s overall geomorphology dominated by uplands, narrow valleys, and drainage corridors. The regional climate is governed by the northeast and southwest monsoon systems, producing three distinct seasons: a rainy season from mid-May to October, a cool season from November to mid-February, and a hot season from April to mid-May. Average annual temperature is approximately 27 °C, with marked seasonal variation, moderate to high relative humidity, and an average annual rainfall of about 975 millimetres, influenced by the rain-shadow effect of the Tenasserim (ตะนาวศรี) mountain range. Vegetation within the park reflects variations in altitude, moisture, and soil conditions, with mixed deciduous forest forming the dominant plant community and covering more than four-fifths of the total area, accompanied by smaller extents of dry evergreen forest and dry dipterocarp forest, while limited areas have been modified by past land use and agriculture. The park’s geomorphological and hydrological features give rise to several prominent waterfalls, most notably Nahm Tok Sai Yohk Lek (fig.), Nahm Tok Sai Yohk Noi (fig.), and Nahm Tok Sai Yohk Yai (fig.), which are integral components of the Khwae Noi river system and contribute to both ecological processes and landscape diversity. In addition, the limestone geology of the region has resulted in the formation of extensive cave systems, including Tham Dao Dung (ถ้ำดาวดึงส์) and Tham Lawah (ถ้ำละว้า), which represent important speleological features and provide specialised habitats for cave-dwelling fauna. Sai Yohk National Park supports high biological diversity, with recorded fauna comprising at least 294 species, including mammals, birds, reptiles, amphibians, and freshwater fish, many of which are associated with forested habitats and riverine ecosystems of the Khwae Noi basin. The park is of particular scientific significance as the type locality for Kitti’s hog-nosed bat, the smallest known mammal species, nicknamed Bumblebee Bat, and it also provides habitat for large mammals such as the Asian Elephant (fig.) and Gaur (fig.), the world's largest wild bovine animal, alongside a rich assemblage of birds, reptiles, and freshwater fish. Collectively, the park represents an important conservation area for mountainous forest ecosystems in western Thailand, contributing to regional biodiversity preservation, watershed protection, and the maintenance of ecological connectivity along the Thai–Myanmar frontier. Usually transliterated Sai Yok and also used as the name of the district or amphur in which the park is located. See also ton sai. WATCH VIDEO (1), (2), (3) and (4). 回