Dokong, Translucent Juicy

Originated from South East Asia, Duku or Langsat is an exotic, seasonal fruit in the tropics and so it is called in Malaysia and Indonesia. The scientific name is Lansium domesticum. Langsat is also known in English as Lanzones. In Thailand, the same fruit is called Longkong. And a local fruit vendor told me the fruit is Dokong!! According to the seller, this variety is sweeter, nicer owing to smaller or undeveloped seeds and thicker rail, so it is very much preferred over the standard Langsat. My wild guess, this is a cultivar between Duku and Longkong, thus gives the name Dukong or sometimes refers to Dokong!

Origin
It originates from western Southeast Asia, ranging from Southern India to the Philippines. It is found easily in Malaysia and Thailand. It belongs to Meliaceae family.
Varieties of Langsat Tree
Varieties of lansium domesticum fruit in Malaysia. Below shown variety and its differential between:

Duku
-round shape with thick pale yellow rind. It is the bigger size than langsat and dukong, sweeter than langsat. It is the biggest size comparable to Dukong and langsat.

Langsat
-egg-shaped fruits with the thin yellowish leathery cover by soft hair, there is latex when peeling off. It is rougher than duku, and green color seed. The flesh was strong bitter taste. It is smaller than dukong and duku

Dokong or Longkong
-The thick rind in pale yellowish color. There is no latex while peeling off. Dokong is a hybrid of duku and langsat with very few seeds. This is the more expensive among Duku, langsat, and Dukong.

Dokong has the combined properties of duku and langsat. The fruit can be elliptical, oval, or round. Each round fruit is covered by yellowish thick, leathery skin. Underneath the skin, the fruit is divided into five or six slices of translucent, juicy flesh.

Reference:
http://www.mywisewife.com/exotic-tropical-fruits-duku-langsat-dokong.html
http://www.malaysiafruit.com/langsat/langsat.php
http://tropicalfruitfarm.com.my/pdf/Dukung-k.pdf