I think Andrew Paul McKenzie Pegman is right. It is known as Lansium parasiticum. Is the fruit look like in the attachment? Its a popular fruit in Malaysia and locally known as Duku or Langsat. And I guess this is Duku.
Langsat - Slender tree with open crown, fruits in clusters of 6-40. Ovoid fruit about 1 inch (2.5 cm) in diameter, thin peel containing latex, sour to sweet. Contains 1-3 green, bitter seeds. Duku - A vigorous, spreading, symmetrical tree with dense foliage, fruit in clusters of 4-12. Fruits are spheroid, 1-2 inches (2.5-5 cm) in diameter, with a thick peel, little to no latex, and a sweet, aromatic pulp. The seed is ellipsoid in shape. Adapted to tropical conditions. 'Du 1' is a Malaysian variety
The easy way go to a group available on Facebook named "Plant identification Group" Upload the pics of a plant and they will out the answer. Botanical expert available in that group will definitely give you the right answer.