It's not longan because not all Dimorcarpus longan is a longan. Murahilin i think nailed it. If i remember correcty there are 4-6 subspecies of D. longan malesianus? Red Durian you need to get a copy of the book Wild Vegetables and Fruits of Sarawak, put out by Sarawak Ag department. It's out of print now but you might be able to get a used copy. i think your fruit is included in that book, plus a lot of others that you are having questions about.