That's what Pakistan tried in Kashmir , how well did it work out ? Moreover , Ahoms are not submissive people , they're fighters and the entire community is licensed with firearms to a great extent and have strong association with the army and police. Invasion of Assam is impossible, even if bangaldeshi population breaches the 50% barrier , nothing will happen. Having been through that area , most Bangladeshis are squatters paying rent to local land owners ,Very few Bangladeshis own any land in Assam , considering that , they're not even a threat. Assam is a highly militarised state , Even if you guys decide to instigate an insurgency India will probably respond with a full scale assault on your military, industrial and economic centres and put you under a naval blockade. That wouldn't end well for you. No one wants war but bangaldesh has much more to lose.
It's not your land , don't even think about coming here. You have your own country to live in. Any hope of bangaldesh conquering Assam is a pipe dream and will remain so except for a few delusional idiots who overestimate themselves by a massive margin.
Let's Respect the boundaries of our two sovereign nations, live and let live
Don't propose anything which violates another nation's sovereignty. Think of development instead of conquering another nation