Two states of two different countries surrounding Bangladesh have a certain degree of seceding from their respective countries to join Bangladesh: Assam, a state in Northeast India, and Rakhine state from southwest Myanmar.
RAKHINE
A full 42% of Myanmar’s Rakhine state, bordering Bangladesh, is ethnically South Asian and speaks a variant of Bangla. The districts of Sittwe and Muangdaw are nearly 95% so, and their persecution in a xenophobic and oppressive Myanmar is well known. They are not welcome there and are considered foreign. Many thousands have fled and have sought refuge in neighbouring countries. Others have been murdered or driven out of their homes. The Rohingya people of Rakhine are predominantly Muslim and have suffered huge massacres in their home state from Buddhists. Thousands have tried getting into Bangladesh through Chittagong, and majority are sent into slum-like refugee camps. If a referendum (like in Crimea), was set up in Rakhine to join Bangladesh was established I would say that there would be a pretty good chance that the people would elect to secede from Myanmar.
ASSAM
It is one of the most insurgency prone regions of India, in the remote region of the Northeast often neglected by the capital. Approximately 1/3 of the population are Muslim, with more and more entering as illegal immigrants from Bangladesh. The influx of settlers has provoked the attention of India's government and Modi. However, in the coming years there would be very little chance of the insurgency ending or the illegal immmigration stopping. Plus, Sylhet, one of the major cities of Bangladesh, used to be part of the state of Assam and themselves held a referendum to join East Pakistan (Bangladesh) in 1947. Assam shares geographical similarities to Bangladesh and their tea and oil industry can thrive along with the added tea exports from Sylhet. Bangladesh can become a huge tea exporter and the exports can go to the direct improvement of Assam, where in India, the state-run industry is being largely distributed to the billion plus population instead of their respective state. Dhaka is also a much closer capital than Delhi, and the Assamese culture largely corresponds with Bengali culture. If Assam wants better development, I believe Bangladesh is the best bet. Plus, the annexation of Assam might be a wake up call to the other states of the Northeast to resist Indian rule and probaby secede, form their own republics, or even join Bangladesh as well. Plus, the seccession/annexation of the Northeast would mean the world to Bangladesh as it would mean that the country would not have to be surrounded by India on three sides, but one. It will also be a huge boost for Bangladesh's trading aspirations with China, Thailand, and Indonesia.
These might be some over-nationalistic aspirations, but if you look at how Bangladesh's economy has been growing at over 6% per year, it might not be such a bad idea. Our secular government should appeal to the minority groups in the regions and it would more than double our area. What do you guys think?