After initial trials, he spent two years at the Bangladesh Krira Shikkha Protishtan (BKSP) under the supervision of local coaches Golam Sarwar Tipu and Rezaul Haq Jamal.

Topu, who was initially selected for training by English coach Anthony Ferguson and England-born Bangladeshi footballer Anwar Uddin, was granted Tk 10,000 scholarship by the Canary Wharf Group after completing its programme.

[15] On 24 October 2014, at the age of 19 years, 11 months, and 5 days, Topu made his debut for Bangladesh national team in a friendly match against Sri Lanka.

[26] On 13 November 2021, during the second matchday of the 2021 Mahinda Rajapaksa Cup, Topu scored an 86th-minute penalty to give Bangladesh a memorable win against Maldives for the first time in 18 years.

[28] On 20 September 2023, customs officials at Shahjalal International Airport in Dhaka discovered that Topu and four of his teammates had illegally imported 64 bottles of alcohol.

This transgression took place following their return from Maldives, subsequent to Bashundhara Kings suffering a 1–3 defeat at the hands of Maziya in the 2023–24 AFC Cup.

[29] Despite the initial indefinite suspension of the players, Topu, who was found to be carrying approximately 26 bottles, was handed a ban lasting two and a half months, until 31 December 2023.