In 2018, Chun turned pro and was the youngest player on the Symetra Tour. The seventeen-year-old was not able to earn an LPGA tour card there, but she did manage to finish tied for 13th in the Q-Series to earn an LPGA card that way. In 2019, she was the youngest player on the LPGA tour.

By and large, it was a struggle for Youngin on tour in 2019: she missed more cuts than she made, but there were highlights. Her best performance came at the Marathon Classic in July. She shot a first round 64, and contended for several more rounds, finishing with her career high tie for 11th. Had she finished just one shot higher, she would have qualified to play in the AIG Women's British Open. She also contended for a couple of rounds in Portland before a bad Saturday round dropped her off the leaderboard, and had a good week at the Dow Great Lakes team tournament.

Youngin finished 126th on the money list and had to return to Q-Series. She managed to earn a category 14 status for the tour in 2020.

In 2020, the whole world was rocked by the Covid-19 pandemic, with the LPGA and KLPGA canceling or postponing many events. Youngin ended up playing just four events in 2020 and made just one cut, a tie for 53rd at the Marathon Classic. Fortunately, she maintained status through 2021, as the tour froze cards for two years to offset the effects of the pandemic. But she only played one LPGA event in 2021 and missed the cut. She only played two events on the Symetra Tour and made no money there, either. The reason: she took a medical deferment for an undisclosed injury. So she continued to have category 14 status on tour in 2022.

Youngin played six LPGA events in 2022, but only made one cut, earning just over $7500 for the year. At the end of the year she revealed that she was suffering from a medical condition that made it difficult for her to compete with the other women. So, she decided to retire. Best of luck to her in her future endeavors!