Bhai there are lower class people in need of jobs in India too who may cross on over to or country. Or you're saying India is a first world country now without lower middle and lower classes?
I know that there are tons of Indian illegals coming over to join our Garments and textile sectors, given those were established sectors in India sometime ago and have seen losses of exports.
I think you and @LuCiFeR_DeCoY got the answer for why india got 4B$ remittance from Bangladesh . If you compare " World Bank said those living in Pakistan sent $4.9 billion to India in 2015 as remittance " . So obviously it's not coming from Indian workers in Pakistan .
I don't know how many Indians are employed in Bangladesh but i know my apartment contractor in southern India has employed labourers from Bangladesh though they say they are from West Bengal , my india Bengali friends say these labourer are Bangladeshis from their accent.