In Berg & Corner’s (2005) monograph on the Figs of Malesia (the botanical region that stretches from S. Thailand to New Guinea), Ficus lowii is listed as a Malay Peninsula endemic. According to Berg (2005) Ficus lowii does not occur in Borneo where it is replaced by two similar figs (1) F. corneri which is very similar to F. lowii but with much smaller leaves and (2) F. soepadmoi which is similar but has long oblong leaves with parallel sides and revolute (turned inwards) edges to the leaf blade.
However it is possible that all 3 species do occur in Borneo.
The photos below from the Leiden Herbarium (Naturalis) collections illustrate the very distinctive appearance of Ficus lowii in Malaya. The dried upper surface of the leaf has a waxy glossy appearance whilst the undersurface is a distinctive whitish or pale grey, unique amongst the Section Conosycea strangling figs apart from Ficus corneri and Ficus soepadmoi.