The herb also called holy basil that gives pad kraphao its name is kraphao, also spelled kaphrao or kaprao. In Thai, the herb is written กะเพรา and is botanically identified as Ocimum tenuiflorum.
Kraphao has a pungent, peppery, clove-like aroma that becomes especially pronounced when the leaves hit a hot wok. Thai cooks use it in stir-fries with pork, chicken, beef, seafood, or rice, most famously in phat kaphrao. Red and white varieties are both used in Thailand, with the red type often described as more pungent.
A common mix-up involves horapha, or Thai basil, which has smoother, sweeter, anise-like notes. Maenglak, usually called lemon basil, is another different basil variety with a more citrusy character. These herbs can appear in Thai dishes, but substituting them changes the flavor and does not alter what kraphao means.
The English name “holy basil” also reflects the plant’s wider cultural history. Ocimum tenuiflorum is important in Ayurvedic traditions and is known as tulsi in India, although Thai culinary kraphao belongs to the same species used in those traditions.