Please name this plant
I believe this plant may be Rotala rotundifolia

Quoting from Wikipedia,


  It is a common weed in rice paddies and wet places in India, China, Taiwan, Thailand, Laos, and Vietnam, and has been introduced to the United States.


This makes sense, as Bangladesh is located near both India and China.


  The emerse form has rounded leaves, the submerse leaves are narrow lanceolate. It is very variable dependent on light and environmental conditions. Under strong light, the leaves can become almost wine red. It has pale pink flowers.