I came across longkong in the durian orchard we visited recently.
“Oooh, longan,” I said, before being corrected by our Thai host that these were in fact longkong.
At first I thought it was a difference only in pronunciation, but after peeling a fruit, I realised this was not the case.
Longan have a single seed surrounded by smooth flesh (like a lychee). Longkong have several separate fleshy segments, looking a bit like a miniature mangosteen when peeled open.
Unfortunately the orchard longkong were not quite ripe yet. The segments were still whitish rather than translucent, and thus a bit sour. However they seemed to be along a similar line to lychees, longan and rambutan – a juicy translucent white flesh with a subtle almost floral taste.