Previous clubs
Heart of Midlothian, Rangers (loan), Inverness Caledonian Thistle (loan), Dundee United, Gillingham (loan), Greenock Morton (loan), St Patrick's Athletic, Northern Colorado Hailstorm& ArbroathBiography
Billy began his senior career at Heart of Midlothian in 2012, progressing through the club’s youth system and making over 80 appearances.
In 2016, he joined Rangers on loan, helping them secure promotion to the Scottish Premiership. Later that year, he had another loan spell with Inverness Caledonian Thistle, before signing permanently with Dundee United in 2017. During his time there, he had short loan stints with Gillingham in England and Greenock Morton.
In 2020, King moved to the League of Ireland, joining St Patrick's Athletic, where he enjoyed a successful spell and won the FAI Cup in 2021. He then made a move to the United States, signing with Northern Colorado Hailstorm in USL League One. In Janaury 2025, he returned to Scotland with a brief spell at Arbroath, before joining Bonnyrigg Rose in the summer of 2025.