Thomson began playing rugby union for his home club Gala. He played for Gala for 3 seasons.[3]
Thomson then played for Melrose. He spent 11 seasons at Melrose making 234 appearances and scoring 106 tries.[3] With the club he won the Scottish Premiership 4 times, the Scottish Cup 2 times and also won the 2011 Melrose Sevens with the club.[3]
In 2011 he played for Sale Sharks but did not make the first team, instead scoring tries for their reserve side.[4]
He secured an Elite Development place with Glasgow Warriors in 2012.[4]
He played twice for the club in season 2012-13, scoring a try.[5] He is Warrior Number 210.[6]
He was vice-captain of the Super 6 side Southern Knights in season 2019-20; playing 9 times and scoring 1 try.[3]
He has been capped by Scotland Club XV and is currently the most capped player to date with 15 appearances.[7] He captained the side in 2018.[7]
On 30 July 2020 Thomson resigned from the Southern Knights to take up the position as Head Coach of Gala.[8] Uncertainty in the timetabling of competitive rugby in the covid-19 pandemic is said to have influenced his decision to stop his playing career.[9]
