Being the runner-up of Miss Southern Region Vietnam, she had the opportunity to compete in Miss Vietnam 2018 and she was selected to the Top 5 along with the Beauty with a Purpose award.
Thùy Tiên was appointed as Miss Grand Vietnam 2021 and later participated at Miss Grand International 2021.[4] She was crowned on November 16, 2021.[5]
During the national costume competition, held on November 30, she wore a costume entitled “Blue Angel” by designer Tín Thái,[6] that featured a pair of huge wings with gilded decorations behind, an elaborated headdress, gloves, as well as bulky platform boots with 8-inch heels that reportedly hindered her walk.[7] However, her costume made strong impression and was positively commented, in spite of another mishap that took place towards the end of her performance when her right wing unexpectedly collapsed,[8][9] leading Thùy Tiên to comment on the incident on her Facebook page: "Thank you so much! There was a little incident with the wings, but I hope everyone will ignore it and support me in the upcoming rounds."[10]
At the preliminary competition, held on December 2, she wore a red dress during the evening gown performance.[11]
On December 4, at the final show, Thùy Tiên was advanced to Top 20.[12] After that, she then wore a blue two-piece bikini at the swimsuit competition that helped her advance to Top 10.[13]
During the English presentation of Miss Grand International 2021, she answered on the topic of world peace. Right after that, she said a sentence in Thai that means "Make the world a better place for everyone", while raising 3 fingers together, a protest symbol greeting, anti-dictatorship inspired by the Hunger Games, is also the salute of pro- democracy protesters in Thailand and Myanmar.[14][15]
During the Top 10 evening gown performance, she wore a dress called "The Crown Dress". This is also the dress chosen by the beauty in the Miss Grand Vietnam 2021 crowning ceremony.[16]
With that answer and her evening gown performance, once again she advanced to Top 5.[17]
During the Top 5 question and answer round, Thùy Tiên was asked by the host, "There are many problems in the world right now, such as human rights and the economy. Who would you choose and why?" She answered:[citation needed]
"If I had a chance to choose who I could talk to, I would like to say thank you to the person who invented the AstraZeneca vaccine. Because she doesn’t need the money to license what she invented. I want to send my thanks to you and everyone to let you know that I am very grateful to you. Because sometimes you choose to do good things. Without requiring credit for what you do, thank you."
After that, with the best interview questions in English and Thai, she won the title and was crowned by Miss Grand International 2020, Abena Appiah.[18][19]
In her capacity as Miss Grand International 2021, she travelled to Thailand,[20] Peru,[21] Ecuador,[22] Colombia,[23] Spain,[24] Angola,[25] Romania,[26] United Kingdom,[27] Malaysia,[28] India,[29] Indonesia,[30] and her home country of Vietnam.[31]
On May 29, 2022, Thùy Tiên made a guest star appearance in Hoàng Hải's fashion show Bướm hoang/Wild Butterfly (the closing show of the Aquafina Vietnam International Fashion Week Spring/Summer 2022), for which she was the showstopper, dressed in a rhinestone, thigh-high split dress with angel wings.[32] However, her left shoelace came loose and gradually slipped down during her walk, which caused her to trip on the 3D butterfly decorations attached to it and fall on the catwalk.[33][34] The incident received widespread attention throughout the Vietnamese media, to the point that Thùy Tiên gave her own comments on what exactly happened.[35][36]