Oommen has acted as lead counsel in dispute work and in particular international arbitrations (both in Europe and Asia) for the last 20 years. He has been lauded for his incisive advocacy and client management skills. He has acted in a wide spectrum of disputes ranging from transport, media, energy (both oil and gas and renewables), infrastructure and corporate shareholding, and has represented sovereigns, state owned entities, multinational companies and high net worth individuals. He has also acted as sole legal advisor in national enquiries.

He has been consistently cited in leading directories and lauded as being “knowledgeable with the ability to reassure the client (Chambers 2014), “a good clear advocate” (Chambers 2015), “accurate in his assessment and displays good tactical awareness” (Chambers 2017) and “helming an arbitration practice par excellence” (Legal 500)

Oommen sits on the Strata Titles Board in Singapore, appointed by the Minister for National Development, which hears disputes involving subsidiary proprietors and management corporations in office and residential strata space. He also teaches as an adjunct lecturer in the Sorbonne- Assas University LL.M. programme and has co- authored a book on arbitration practice in Singapore and another book on court rules.