In the 2016 U.S. Junior Amateur Championship, Lee made a late rally in bad weather conditions at The Honors Course in Tennessee to defeat Noah Goodwin, 16, of Corinth, Texas, 2 and 1.

Four years before that, Lee’s older sister, Minjee, claimed the U.S. Girls’ Junior title, which, according to the USGA, makes them the only brother-sister tandem to win USGA Junior championships.

Lee turned professional at the start of 2019 and finished fourth in the Saudi International and T5 in the ISPS Handa World Super 6 Perth; in October, he was T6 in the Genesis Championship on the Korean Tour. 

In February 2020, he won the ISPS Handa Vic Open, an event co-sanctioned by the European Tour and the PGA Tour of Australasia.

In July 2021, Lee defeated Thomas Detry and Matt Fitzpatrick in a playoff at the Abrdn Scottish Open. With this win, he earned entry into the 2021 Open Championship. In May 2023, Lee earned a special temporary membership on the PGA Tour.

In October 2023, Lee won the SJM Macao Open on the Asian Tour. He shot a tournament record of 254 at 30-under and won wire-to-wire.. One month later, Lee won the Fortinet Australian PGA Championship.

Amateur wins

2013 Drummond Junior
2014 Drummond Junior
2015 Western Australia Amateur, Drummond Junior, Aaron Baddeley International Junior Championship
2016 U.S. Junior Amateur
2017 Western Australia Amateur
2018 South Australia Amateur Classic