Thomas will be the US ad technology start-up's first UK hire since Stevens joined in June. Reporting to Stevens, who is vice-president and general manager, international, Thomas will be responsible for supporting publishers in the UK to help them generate ad revenue around inventory.
He joins from online price comparison service Xelector, where, as commercial director, he implemented partnerships with publishers such as MSN and The Telegraph.
Previously, Thomas spent seven years at AOL Europe in sales and business development roles, creating online advertising initiatives, including microsites and targeted sponsorships for Interflora, DatingDirect, GAME and Blockbuster.
Rubicon, a full-service creative marketing agency, sells proprietary advertising systems. It places advertisements on major networks such as Yahoo and Google.