After returning to Australia from his interventional fellowship in Queen's University, Canada, in 2005, Thomas worked as an interventional cardiologist for Barwon Health from 2005 to 2019. His private practice is based in Geelong. His interests include general and interventional cardiology, new device therapy for coronary artery disease and structural heart disease, and renal denervation for resistant hypertension. He is accredited for reporting in CT coronary angiography. He is an examiner for the Royal Australasian College of Physicians where he has been involved in physician training. He is the principal site investigator for international trials such as CLARIFY and Global Symplicity Registry. His other research interests include high sensitivity cardiac troponin. In 2015, he undertook a sabbatical to learn transcatheter interventional management of structural heart disease in the University Hospitals of Leicester, UK, developing experience in TAVI (transcatheter aortic valve implantation) and LAA (left atrial appendage) closure.