Native to South America, the papaya, or pawpaw, has been adopted by Thai cooks. The two main varieties available in Thailand are khak nuan, a blunt cylindrical papaya with a yellow skin and sweet orange flesh, and wuak dam, also cylindrical but with a pointed end. Its skin and sweet flesh is reddish.
Ripe papaya is often served simply sprinkled with lime juice. The unripe fruit is usually treated as a vegetable, and may be boiled or enjoyed raw in salads or as a relish.
Choose ripe fruit that is uniformly orange or, if you do not plan to use it straight away, slightly firm fruit with green skin that is turning orange. The fruit will continue to ripen in a dark place. Avoid bruised or shrivelled fruit and handle with care, as papayas are easily damaged. Ripe papayas will keep for about 1 week in the refrigerator.