The 23-year-old Thai was familiar with her opponent, having sparred with the Filipino during training in Nakhon Ratchasima ahead of the Games.
She relied on her knowledge of Magno’s style to dictate the fight with accurate blows and left hooks that won her a unanimous decision.
The 2019 SEA Games bronze medallist from Nakhon Si Thammarat became the second Thai boxer to reach the quarter-finals at Tokyo, following in the footsteps of Chatchai-decha Butdee in men’s 57kg division a day earlier.
“I was quite confident going into the fight because we trained together and I never lost to her. I could box at will and did everything according to my plan,” said Jutamas, who only took up boxing four years ago.
“Actually, it’s been tough for us as we barely had any warm-up tournaments because of the COVID-19 situation. Some of us were a bit rusty at the beginning.”
Up next for Jutamas is top seed Buse Naz Cakiroglu of Turkey who beat Tursunoy Rakhimova of Uzbekistan 3-2.
Jutamas is eyeing revenge against the Turk, who won their only previous encounter. A winner in the quarter-finals is assured of at least a bronze medal.
“I lost to her in a close fight in the Czech Republic. I think she was more dangerous back then. Now, I’m quite confident and I will try my best to get an Olympic medal,” she said.
The bout is scheduled for Sunday as is Chatchai-decha’s quarter-final clash with Lazaro Alvarez of Cuba.
In shooting, 58-year-old Svate Sresthaporn, after a strong start on Wednesday, missed three targets and a place in the six-athlete final in the men’s trap competition.
He finished 17th with 121 points.
Jazz one off lead
In the men’s golf tournament, Thailand’s former Asian Tour Order of Merit winner Jazz Janewattananond is one shot off the lead behind Austrian Sepp Straka after a weather-interrupted first round yesterday saw home favourite Hideki Matsuyama and British Open champion Collin Morikawa suffer frustrating starts.
World number 161 Straka took advantage of early benign conditions to set the pace with a bogey-free eight-under par 63 at Kasumigaseki Country Club.
Matsuyama and Morikawa both finished at two-under par 69, either side of play being suspended for more than two hours in the afternoon because of a lightning storm.
Another Thai hope Gunn Charoenkul began his campaign with an even par 71.