Thomas is an expert on corporate finance and corporate governance. His work has influenced both academic thought and business practice. 

Thomas explores the effects of risk and incentives on the design of governance systems, contracts and financial networks. His work has influenced the way companies are financed through the issuance of securities, contributed to the way we analyse systemic risk for firms, and provoked a re-evaluation of the way senior managers are compensated. His work has appeared frequently in all leading finance journals and so many leading economics and management science journals. Currently he serves on the editorial board of the Journal of Corporate Finance, Journal of Banking and Finance, and the Journal of Economics and Management Strategy.

Prior to joining Saïd Business School, Thomas held the AB Freeman Chair in Finance at Tulane University. He is a professorial fellow at Balliol College, and a research associate at the Oxford-Man Institute and the Centre for Corporate Reputation at Oxford University, and the European Institute for Corporate Governance.