Thomson missed Saturday's goalless draw with Dundee United in the Scottish Premier League through suspension but is back in contention for the second round clash.
However, Chris Innes is set to sit out the visit to Somerset Park after picking up a hamstring strain.
St Mirren (from): Gallacher, Ross, Mair, Potter, Barron, McGinn, Dargo, Dorman, Brady, Mehmet, Higdon, Brighton, Howard, Robb, Faulds, Quinn, Murray, Thomson.







