Khor entered politics when she contested as part of a five-member People's Action Party (PAP) team in the 2001 general election in Hong Kah GRC.

[4][5] During the 2006 general election, Khor joined a five-member PAP team contesting in Hong Kah GRC again and they won by an uncontested walkover this time.

In the 2011 general election, Khor contested as a solo PAP candidate in the newly formed Hong Kah North Single Member Constituency (SMC) and won with 70.61% of the vote against the Singapore People's Party's Sin Kek Tong.

[6] During the 2015 general election, Khor retained her parliamentary seat in Hong Kah SMC after winning 74.76% of the vote against the Singapore People's Party's Ravi Philemon.

In the 2020 general election, Khor retained her parliamentary seat in Hong Kah SMC after winning 60.99% of the vote against the Progress Singapore Party's Gigene Wong.