He represented the New Zealand All Blacks between 2008 and 2012, playing a total of 29 tests including two during the victorious 2011 Rugby World Cup campaign.

[1] He attended Christchurch Boys' High School, and played in the same 1st XV side as fellow All Black Dan Carter.

2006 saw Thomson move to number 8 where he played five matches, including try-scoring appearances in the 56–21 win over North Harbour, and against Southland.

He played in twelve matches, scored five tries (including one in the victory over the Crusaders), and ultimately made the All Blacks squad that year.

[8] Thomson was selected for the All Blacks in June 2008, making the squad ahead of Kieran Read, who was also waiting to debut in test rugby.

In 2009 he started the international season at openside flanker, filling in for captain Richie McCaw, before breaking his thumb 30 minutes into the game.

Thomson was side-lined for the better half of the season before making his comeback against Australia in the final Tri-Nations match, playing at blindside flanker.

In 2010 he made the squad for the early-season Steinlager Series against Ireland and Wales, but not the Tri-Nations or end-of-year grand slam tour.

[15] He played 15 matches in the season, finishing as the team's top tackler and the competition's second-most prolific winner of opposition lineouts.