It’s possible to put together a quite pleasant run combining Rama Park, Shishu Park, and some adjacent spots. The 70-acre Ramna Park is one of the signature places to run in Dhaka. There are long pathways passing by numerous species of flowers, trees, and other greenery. There’s a small lake at the center. A loop of the park’s paths is 2.4 km. Adjacent to Ramna Park, you can add with a small loop along outside perimeter paths of Shishu Park (small amusement park), and then cross over to the grounds around the Eternal Flame and the Museum of Independence. (Suhrawardy Udyan). This section is a 1.5 km loop. In all, it’s ~5.5 km.
Longer Run/Add-Ons: Adjacent to Suhrawardy Udyan is the University of Dhaka, which has some decent pedestrian paths away from the busy road. For an even longer route, you could run through the campus of the university to Dhanmondi Lake (see our route there).