Identification of a moth
It looks like a Hesperiidae (Skipper), not a hawk moth (Sphingidae). There are more than 3500 species of skippers worldwide though, and I don't know what species this is. However, I'm sure that somebody who knows butterflies in Bangladesh could identify this to the genus level.

One suggestion/guess/starting point might be Baoris pagana, but this is merely based on a quick glance at skippers found in India.


(picture from http://www.ifoundbutterflies.org/)