I have seen this insect flying literally everywhere in Dhaka city (Bangladesh) over the last two months. It's small -- around 1-1.5 inches long. It's not an agile flyer and can be easily grabbed by hand during flight.
This is actually the flying adult of a scale insect (superfamily Coccoidea). Specifically, this appears to be some species of the genus Drosicha.
Here is a picture resembling your specimen:
Source: John Horstman
And another from Vietnam that looks very similar:
Source: Dan Doucette
I can only find info on a closely related species, Drosicha corpulenta, and here's a tree of related species.
Scalenet provides numerous keys and references that could be useful for positively IDing this specimen.
I will keep searching for more details, but this might be the best you get without asking a scale insect expert.