The REDD scheme of the United Nations Framework Convention on Climate Change is a carbon-based compensation for projects that resulted in reducing carbon emissions or enhancing carbon sinks or both in tropical forests. However, estimating such emissions and sinks remains challenging, and thus making it impossible to estimate carbon revenues from managing tropical forests. Here, we estimated the reduced emissions and sinks by developing models for setting Reference Emission Level (REL) and Project Emission Level (PEL) for REDD projects in concession forests taking emissions under conventional logging (CVL) scenario as that of REL, and emissions under reduced impact logging (RIL) and RIL with liberation treatment (RIL) scenarios as that of PEL. By choosing Cambodia as a case study, REL under the current logging system of 25-year cutting cycle was estimated at 23.1 TgCO2 year-1. To determine an appropriate cutting cycle, we tested our models with four cutting cycles and found that a 50-year cutting cycle is more appropriate. Taking this 50-year cutting cycle for REDD project, PELs were estimated at 0.4 TgCO2 and -3.3 TgCO2 year-1 under RIL and RIL, respectively (- means sinks). After subtracting REL with PEL and leakages, annual carbon credits from managing 3.4 million ha of concession forests in Cambodia were estimated at 15.9-18.5 TgCO2 depending on chosen scenario. With a carbon price of $5 MgCO2-1, total revenues from the sales of carbon credits alone are $79.5-92.5 million annually. To ensure continued flow of wood supply from tropical forests while mitigating climate change, we suggest that new climate agreements adopt RIL or RIL for sustainable forest management in tropical countries.