In November, Haeji played in the Futures Tour Q-School, where she finished tied for 12th. Thus, she turned professional. In 2008, she finished tied for 14th at the ANZ Ladies Masters, a good omen in preparation for her move to the States.

In 2008, she played the Futures Tour, where she made over $30,000 and finished just outside of the top ten on the money list. This is important, since a new rule change made it so the top ten players on tour received cards for the LPGA. She had six top tens, including her first professional win in Richmond, Virginia, in August.

In late 2008, Haeji Kang participated in the 2008 LPGA Qualifying School. She finished tied for 29th to earn category 16 status on tour in 2009.

Haeji had an OK rookie season despite her low status on tour, highlighted by a great performance at the Wegman's, where she shot her career low round and finished tied for fourth. This top ten and a few other good weeks were enough to earn Kang a full exemption for the 2010 season.

In 2010, she made the most money of her career, finishing 59th on the money list to keep her card. She had one top ten, at the Sybase Match Play. Her best finish in the 2011 season was 14th; she finished 77th on the money list that year, keeping full status for 2012.

Haeji improved enormously in 2012. It was in fact by far her best season yet. She finished 29th on the money list with over $400,000 in earnings and four top tens. She had her first top 20 in a Major at the Nabisco, and her career best finish of third at the Navistar. Her scoring average was also her best by a lot. With her 2012 season results, Haeji Kang has put herself on the radar as an up and comer for the first time.

Her 2013 results were pretty similar to her 2012 results. She still wasn't able to get a win, but did manage three top tens and more than $400,000 in earnings, good for 37th on the money list. Her most notable achievement was her tie for 5th at the Kraft Nabisco Championship, her first ever top five at a Major.

Haeji had two top tens in 2014, both ties for third place, at the Reignwood LPGA Classic and the ShopRite Classic. She finished 49th on the money list for the year.

Kang had a markedly worse season in 2015 than in her previous years. She was not able to make even a single top ten and only made $44,000 for the year. As a result, she dropped to category 16 status for 2016. Her 2016 season was about the same, with her best finish a tie for 20th. She dropped even further to category 17 status for 2017.

Haeji had a lackluster 2017 season, but managed one great finish, a tie for 5th at the Indy Women Tech Championship. As a result, she made about $90,000 in 2017 and finished 89th on the money list. This moved her up to category 16 for 2018.

Haeji had her best season in a while in 2018. She made over $258,000 and finished 70th on the money list, which gained her top status for 2019. She had two great finishes: a tie for 9th in Arkansas thanks to a final round 63, and a tie for third at the Scottish Women's Open.

2019 was a less successful year for Haeji. She finished just 104th on the money list and had no top tens during the year. She made $116,000 for the year. Her status was reduced to category 14 for the 2020 season.

In 2020, the whole world was rocked by the Covid-19 pandemic. The LPGA and KLPGA tours canceled and postponed many tournaments. Haeji played 11 events in 2020, missing just two cuts. Her best result was a tie for 28th at the WalMart Arkansas Championship in late August. She made about $60,000 all year, 101st in the rankings. However, the LPGA had decided to let all players keep their cards through 2021, so she will maintain the same playing status as before.

Haeji had a solid year in 2021. She finished 78th on the money list, improving to category 11 for 2022. She earned about $221,000. Her best finish, and only top ten, was a t-6th finish at the Dow Invitational team event.

Haeji played similarly in 2022. She had just two top tens; once again, one of them came at the Dow team event. She made about the same amount of money as the previous year, about $214,000, but that was only good for 92nd on the money list. This allowed her to maintain her category 11 status for 2023.

Haeji made $112,000 in 2023, 126th on the money list. She didn't play an event past July, suggesting she was injured much of the season. And indeed, because of a medical deferment, she maintained her category 11 status for 2024.