Mammals of Kubah National Park Sarawak

Flying Fox perhaps?

Family of Fruit Bats (all five of them) cuddled up and perched upside-down on top corner of wooden beam in the hut next to the world-renown frog pond of Kubah National Park, Sarawak.

Guessing that this is a Giant Squirrel based on quick reading of the Guide to Mammals of Borneo as illustrated by Karen Philips. Couldn't snap a picture of its head in time as this squirrel was bounding actively along the top branch of this forest tree in Kubah National Park, Sarawak.