Tam earned the victory in the round of 16 in the 48-50 kilogram category, in which Nazym won the world championship in 2014 and 2016.
Nazym was also crowned Asian champion in the 50-52 kilogram category in 2021 and finished third in Asia in the 48-50 kilogram category last year.
But Tam managed to claim a perfect victory, taking advantage of her height and long arms to keep the opponent from coming close. All her punches and hooks were effective.
After three rounds, the 29-year-old Vietnamese fighter was declared the winner, with four out of five judges giving her the maximum score of 30.
Tam will fight Modukanele Bokamoso from Botswana in the next round on Tuesday afternoon.
The Women’s World Boxing Championship is being held in New Delhi from March 15 to March 26, attracting fighters from 65 countries and territories for a US$2.4 billion prize pool.
Vietnam sent nine boxers and six have been eliminated, leaving Tam, Nguyen Thi Ngoc Tran, who beat Bulgarias Poptoleva Venelia, and Nguyen Thi Thanh Thao, who beat South African Mnguni Sbusisiwe in round of 16.
Tam, from the northern province of Ninh Binh, is expected to win a medal at the tournament.
She won the Asian title in the 50-52 kilogram category in 2017, 48-50 kilogram category in 2022, and ASIAD bronze medal in 2018. She also won two SEA Games gold medals in recent events.