After completing her undergraduate career, Suh taught earth science in high school. At the time, she believed that teaching would be her chosen career. However, after a few years of teaching, Suh decided to reconsider whether or not the education field was where she wanted to be. After some soul-searching, Suh decided to return to her hometown. Upon her return to Boulder, Suh found work as a waitress, but she continued to look for opportunities to learn about different sectors of the environmental field. She had long been interested in politics and decided to volunteer for an elected official. Through a series of events she attributed to “random luck,” she was hired by Ben Nighthorse Campbell – a new U.S. Senator from Colorado – to be his state representative on environmental issues. In Colorado, Suh worked on federal environmental issues like Clean Air and Water Act violations, Superfund sites, decommissioning of the Rocky Flats nuclear facility, and public lands. She was ultimately transferred to Campbell’s Washington D.C. office to serve as a legislative assistant assigned to cover the Energy and Natural Resources committee. Her experience there was invaluable. It gave her an in-depth perspective on how policy is crafted and an understanding of the politics around environmental issues. However, it was also difficult. Senator Campbell switched political affiliations during her tenure, which Suh characterizes as “a valuable exposure to different perspectives” and “personally challenging.” Ultimately, Suh decided to take a break from politics and to return to the education field. She went to Harvard University to obtain a master’s in education.

After completing her graduate education at Harvard University, Suh worked for private foundations dedicated to environment policy and conservation. From 1998 to 2007, she worked at the William and Flora Hewlett Foundation. In this role, Suh designed and led a climate change and green energy initiative that led to the creation of a land-protection campaign for the Great Bear Rainforest. She also launched New Constituencies, a portfolio dedicated to environmental issues for underserved populations in the United States. In 2007, she started working for the David and Lucile Packard Foundation. While at the Packard Foundation, she created and managed a $200 million program focused on conservation in the West. Suh’s work included developing the Packard Foundation’s strategy to reduce deforestation-related climate change emissions. Suh collaborated with nonprofits to coordinate conservation efforts throughout the Colorado River Basin—from the headwaters in Colorado to the delta in Mexico.

In 2009, after her roles at the two foundations, Suh was nominated by President Obama to work at the U.S. Department of the Interior as  Assistant Secretary for Policy, Management, and Budget. Suh was nominated and confirmed for the government appointment in 2009. She led several cross-cutting initiatives at the department, including creating a new interagency program to develop national conservation priorities for Land and Water Conservation Funds disseminated by the National Park Service, U.S. Fish and Wildlife Service, Bureau of Land Management, and U.S. Forest Service. With her diverse portfolio, she successfully led the Administration’s effort to create a federal recognition effort for the Native Hawaiian community.  In 2011, she co-led the complex reorganization of the agency responsible for offshore oil and gas oversight during the Deepwater Horizon oil spill. After the Deepwater Horizon oil spill, Suh co-led the restructuring of the Minerals Management Service. Suh assumed responsibilities for the Office of Natural Resource Revenue, including collecting oil and gas royalties and fees, which averaged $10 billion annually, on behalf of the federal government. In 2013, President Obama nominated Suh as Assistant Secretary for Fish, Wildlife, and Parks at the Department of the Interior. The nomination faced staunch opposition from Senate Republicans.

In 2015, Rhea joined the Natural Resources Defense Council (NRDC) as its president. Under her leadership, the organization’s revenue grew by over $50 million. NRDC’s membership also increased by more than 40 percent, and its social media following expanded by 230 percent, making NRDC the highest subscriber rate of all environmental groups.  

Suh advanced several initiatives over her four-and-a-half-year tenure at NRDC, including a new ten-year strategic plan and a new internal organizational structure. She also helped steer high-level discussions culminating in the historic global Paris climate agreement. Additionally, Suh advocated for a landmark settlement for Flint, Michigan residents to ensure an end to the city’s toxic drinking water crisis and spoke at the 2017 Women’s March on Washington, D.C. She stepped down from her position as president on June 30, 2019.

After leaving NRDC, Suh was an independent consultant to foundations, nonprofit organizations, and Fortune 500 corporations. She advises on various environmental, sustainability, management, DEI (diversity, equity, and inclusion), and political strategy needs. Starting in September 2021, Suh became the President and Chief Executive Officer of the Marine Community Foundation.

Suh shares her environmental and public health expertise with frequent media contributions. Her work appears in the New York Times, MSNBC, Los Angeles Times, Washington Post, NPR, and other outlets.