How are people from Asia depicted in Bababec by Voltaire?

This is an interesting question, which points towards larger themes important to the time period of the Enlightenment itself. Be aware, European artists and authors possessed a certain fascination with foreign cultures. We see this in works like Mozart's Abduction from the Seraglio or Montesquieu's famous Persian Letters.
However, that being said, we should be aware that this fascination was shaped by exoticism, and it involved tendencies towards judgment. The Enlightenment represented a celebration of European societal and intellectual progress and, in its focus on the rational and the categorical, this is reflected in its treatment of race and culture, where non-European peoples were often found lacking by contrast.
If you were to turn to Voltaire's "Bababec," you would find those same themes are very much in play. Be aware, Voltaire's depiction of India is utter make believe. Their beliefs are portrayed as base superstition, to such a degree as to be absurd, and the same goes for the entire world which they inhabit.
Consider how Voltaire depicts Hindu beliefs. One holy man is interrupted while reading a holy book. He voices outrage, convinced that the resultant disruption would result in him being reincarnated as a hare instead of a bird. Meanwhile, there are the Gymnosophists, who are described as driving nails into their bodies so as to honor Brahma. Finally, there is the character of Bababec himself. In the story, Bababec, a respected mystic, gives up his superstitions, but in so doing he loses the esteem of the community around him.
Ultimately, this story is not all that extraordinary by the standards of the Enlightenment in its treatment of other cultures. Europeans assumed themselves to represent a high-water mark, and they judged the rest of the world according to those standards—and usually judged them poorly. We see this same theme on display in "Bababec," where India is depicted largely in terms of the exotic and as a place dominated by superstition and irrationalism.