Hot spring, specified as temperature higher than 37 °C, manifest as warm-hot pool, boiling and geyser. The water is clear,
colorless with white algae, white-yellow and red scar of calcium carbonate, sulphur and iron disseminate on soil and rocks.
Chemical analysis discloses that hot springs yield pH 6.4-9.5, total dissolve solid 130-24,800 ppm, alkalinity of bicarbonate
47-1,079 ppm and fluoride 0.055-20.4 ppm. Nine hot spring areas, situated within 5 km. away from sea shore in southern
Thailand are saline. Geothermometer calculation using silica, calcium and potassium contents denotes subsurface
temperature of the five highest reservoir temperature ranges 180-210 °C.
Hot springs are considered to be of non-volcanic origin as inferred from isotopic relationship between δD and δ18O. The
chemical contents are characterized by high alkali-sodium and bicarbonate but low concentrations of dissolved chemical
species (Takashima and Kawada, 1981; Kita, 1989). Hot springs located in northern and western Thailand yield fluoride
content higher than 5 ppm and spread out rotten smell of H2S and sulphur.