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.
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