Prior to entering politics, Kwong worked in a youth centre in Long Ping Estate, Yuen Long. In 2004 he became a community officer for Democratic Party's Yuen Long District Councillor Zachary Wong and subsequently joined the party. In 2007 District Council elections, 24-year-old Kwong ran in Pek Long of the Yuen Long District Council, defeating a veteran pro-BeijingDemocratic Alliance for the Betterment and Progress of Hong Kong incumbent Chan Siu-kay. He went on to be re-elected in 2011, 2015, and 2019. As a 25-year-old, Kwong became the youngest candidate in the 2008 Legislative Council election, running in New Territories West with Cheung Yin-tung but was not elected. In the 2012 Legislative Council election, he ran with party chairmanAlbert Ho in the territory-wide District Council “super seat” and successfully helped Ho to be elected. Kwong is also a romantic fiction writer. He published his successful debut book Love You Like the First Time We Met in 2014. His second book, There is a Kind of Happiness Called Forgetting, sold more than 10,000 copies at the annual Hong Kong Book Fair in the same year. He also drew attention online after he published a short love essay entitled "The Last Time You Get" on Whatsapp on the internet in 2012. Kwong had attracted over 92,000 "likes" on Facebook since the essay. Up to 2015, he has published seven romantic novels. His peculiar writing style is imitated and called “Kwong-style”. In the 2016 Legislative Council election, he became a member of the Legislative Council of Hong Kong through the District Council "super seat" with veteran James To in which he won nearly 500,000 votes, the largest votes ever to be received by a ticket. He was once considered as a marginal candidate in the election according to the election poll. However, the weaker pro-democracy candidates from Civic Party, Neo Democrats and ADPL openly suspended their election campaign in order to secure the third super seat of the Pro-democracy camp. Besides, he was recommended by Benny Tai's ThunderGo plan. As a result, Kwong was elected with a record-breaking number of popular votes. Kwong has been a "familiar face" during the 2019–20 Hong Kong protests. He is often seen chanting protest slogans and calling on protesters and police alike to remain calm. On the morning of24 September 2019, Kwong was assaulted near his Tin Shui Wai home. Three people pulled him from his car and began punching and kicking him, with one of them filming the attack. He was subsequently taken to Tin Shui Wai Hospital with injuries to his cervical vertebrae, as he was kicked in the back of the neck. The Democratic Party condemned the incident, alleging it to be an organised attack intended to intimidate supporters of the protest movement. Yuen Long district councillor Zachary Wong claimed that both he and Kwong had received threatening letters a month prior. The Hong Kong government condemned the attack and said the police would investigate.
