Thomas has performed, recorded and broadcast with the Manchester Camerata, the Scottish Chamber Orchestra, the BBC National Orchestra of Wales and the Orchestra of Opera North, and has played guest principal with the Hallé Orchestra, BBC Philharmonic, the City of Birmingham Symphony Orchestra, Royal Northern Sinfonia, Royal Philharmonic Orchestra and Manchester Concert Orchestra.

Since 2011 he has held the post of Principal Second Clarinet / E-flat Clarinet with the Royal Liverpool Philharmonic Orchestra. Highlights with the RLPO include tours to Spain, China and Japan, and playing principal clarinet in the BBC Proms 2013 and the closing concert of Prague Spring Festival 2015.