Provide links for this claim.
I am on a tablet with little access to a PC but what you need to do is google BD arms imports and you will see that it roughly averages around 500 million dollars a year over the last 5 years. The defence budget is only for salaries, maintenance, operations and insignificant locally produced weapons. I calculated a while back that it was between 1.6-1.7 % of GDP when arms imports was taken into account.
Total defence spending tends to rise sharply with Awami League governments as they spend much more money importing weapons than BNP does.