Ling began his career at Leyton Orient, progressing through the O's academy to become Youth Team captain and also featured on the bench for the first-team a number of times.[3] He moved to Dagenham & Redbridge in 2016. On 7 February 2018, he returned to fellow National League and former club Leyton Orient for an undisclosed fee, signing a two-and-a-half-year contract.[4] Ling was one of a number of players to leave Dagenham due to the club's financial issues.[5] His father, Martin, was also director of football at Orient.[4] He made his long-awaited debut for the club on 17 February, coming on as a substitute in the second-half against Chester.[3] He scored his first goal for the club on 15 March 2019 in a 3–2 away win at Barrow.[3] He played a key role at right-back as Orient won the National League title at the end of the 2018–19 season.[5] Ling started the 2019–20 season well and was nominated for the Orient's Player of the Month award in August.[3] On 9 September 2019 he signed a new one-year extension to his contract until the summer of 2021.[6] He had been an ever-present in the side since promotion and their return to the English Football League.[6] He made his 50th appearance for the club on 21 September 2019 in a 2–1 defeat to Colchester United.[3] He made a total of 87 appearances for Orient in three and a half seasons before he was released in the summer of 2021 following the expiration of his contract.[7]
On 9 July 2021, Ling returned to National League side Dagenham & Redbridge on a free transfer.[7] Daggers boss, Daryl McMahon, spoke of his acquisition, "He obviously comes from a good footballing family, with his dad Martin. I've known Sam since he was about five or six, from when I played for Martin at Leyton Orient. He's been at the football club before and did really well here, so we know what we're getting."