Biswamoyopterus laoensis has reddish, grizzled fur with white above. Its crown is pale grey, its patagium is orangish and its underparts are white.
Biswamoyopterus laoensis has one of the greatest lengths in the squirrel family, with a body length of 0.46 m (18 in) and a tail length of 0.62 m (24 in), for a total length of 1.08 m (43 in), along with a mass of 1.8 kg (4.0 lb).[3][4] This is slightly larger than the one other Biswamoyopterus species, B. biswasi, known from a single sample found in India in 1981.
^Sanamxay, Daosavanh; Douangboubpha, Bounsavane; Bumrungsri, Sara; Xayavong, Sysouphanh; Xayaphet, Vilakhan; Satasook, Chutamas & Bates, Paul J. J. (2013). "Rediscovery of Biswamoyopterus (Mammalia: Rodentia: Sciuridae: Pteromyini) in Asia, with the description of a new species from Lao PDR". Zootaxa. 3686 (4): 471–481. doi:10.11646/zootaxa.3686.4.5. PMID26473234.