Bangladesh's Overseer Mehidy Hasan Miraz forced Gunathilaka, Sri Lanka, into the air in his first and second attacks.
Tamim Iqbal went to the left and swung easily to provide a good start for Sri Lanka's final for the Rocket Triangle Series.
Previously, Rankin captain Chandler won an important toss and decided to hit the ball first Saturday at the Cher-Cro-Cratti National Cricket Stadium in Dhaka Millspole.
Sri Lanka: Danushka Gunathilaka, Upul Tharanga, Kusal Mendis, Dinesh Chandimal (c), Asela Gunaratne, Niroshan Dickwella (w), Thisara Perera, Suranga Lakmal, Lakshan Sandakan, Akila Dananjaya, Dushmantha Chameera, Nuwan Pradeep, Dhananjaya de Silva, Shehan Madushanka , Wanidu Hasaranga.
Bangladesh: Tamim Iqbal, Anan Haake, Shabab Hassan, Mushkur Rahim, Madhadullah, Sabir Rachman, Abu Hassan, Nassi Al Hussein, Marsav Moulthard, Huber Moussafir Rahman Hashim Mohammed Saeeduddin Islam, Muhammad Mithun and Imrul Kayes.