Thai basil, or Asian basil ( Oriya: Karpura-kaanti, Durlabha, vibhoothi pachai in Tamil) is a type of sweet basil native to Southeast Asia that has been cultivated to provide distinctive traits. Its flavor is more stable under high or extended cooking temperatures than that of sweet basil. Thai basil exhibits small, narrow leaves and purple stems, with a mauve (pink-purple) flower. One cultivar commonly grown in the United States is 'Queen of Siam'.
Three types of basil are commonly used in Thai cuisine. Thai basil is the cultivar most often used for Asian cooking in Western kitchens. The English common name is Thai basil, but in Thai kitchens, the plant is called bai horapha or simply horapha. Thai holy basil, also called bai gka-prow or kraphao, which may be the basil Thai people love most, is a variety of Ocimum tenuiflorum. The third species of basil found in Thai cooking is the least used, and has undertones of lemon in both scent and taste. Thai lemon basil is called bai maeng-lak or simply maenglak.
Basil is used in several different Asian cultures. Thai holy basil is a variety of tulasi, which is worshiped in India and is also often called "holy basil". Both Thai holy basil and tulasi have smaller, softer, slightly hairy leaves and an aroma akin to that of cloves. In Vietnam, the most common basil cultivar with purple stems is called cinnamon basil; its name describes its flavor and scent.
Although Vietnamese, Cambodians, and Laotians also use the Asian varieties of basil in their cuisines, the purple-stemmed, licorice-flavored leaves have come to be identified as Thai basil. It may be mistakenly called anise basil or licorice basil, but it is different from the Western strains bearing these same names. Horapha leaves are a frequent ingredient in Thai green and red curry, while the basil used in Thai drunken noodles, and Thai chicken/pork/seafood with basil leaf is kraphao. Thai basil is also an important ingredient in the very popular Taiwanese dish, sanbeiji. Used as a condiment, a plate of raw Thai basil leaves is often served as an accompaniment to Vietnamese-style noodle soup so each customer can season it to taste with the anise-flavored leaves.