Tropical Forest Conservation Reauthorization Act of 2018 This bill renames the Tropical Forest Conservation Act of 1998 as the Tropical Forest and Coral Reef Conservation Act of 1998 and otherwise revises the Act. Coral reef ecosystems are included within the Act's scope and made eligible for benefits under the Act. The Tropical Forest Facility is renamed the Conservation Facility, and the Tropical Forest Fund is renamed the Conservation Fund. One or more individuals appointed by the U.S. government may serve on oversight bodies for grants from a debt-for-nature swap or debt buyback regardless of whether the United States is a party to any agreement between the eligible purchaser and the government of the beneficiary country. A grant of more than $250,000 must be approved by the U.S. government and the government of the beneficiary country.