This fabulous little book  A Guide to the Fabulous figs of Singapore (2005)  is a very useful starting point to identify the most common figs of Borneo.

Some 15,000 years ago Borneo and Singapore were connected by the swampy Sunda Basin. This land bridge is currently drowned under the South China Sea but it is not surprising that Singapore and Borneo share many species of figs.

One entry in particular however has caused  much confusion;

Figs of Singapore book
This entry most likly refers to Ficus subgelderi NOT Ficus sundaica.