According to Berg (2005) Ficus obliqua is a common giant fig of New Guinea and Northern Australia  found east into the Pacific including New Caledonia, Fiji, Tonga and Samoa.  The nearest this fig occurs to Borneo is Ternate in the Moluccas. This fig was probably brought to Brunei as an ornamental or bonsai.

Photo credit Tuan Husini thanks to Shavez Cheema