Oil spills cause serious problems not only to the environment, but also the economy. To predict movement of oil spill in a sea, it is necessary to know the current pattern and wind information. However, this information was obtained by observed stations which did not cover the study area; therefore, mathematical models calibrated by observed data were used to simulate current in the study area. The aim of this study was to simulate oil spill in Rayong coastal area using the numerical models. The oil spill simulation model in this study contained 3 sub-models. The SWAN model was used to simulate wind waves. The Delft3D model was used to simulate tidal current and wind induced current. The GNOME model was used to predict the movement of oil spills in the study area. In the simulation of the oil spill, the study was divided into two parts: the first part simulates waves and currents in the Gulf of Thailand. The net current was used to predict the movement of oil spill in the second part.The significant wave height from the SWAN model was calibrated and verified by wave data from 6 GISTDA’s buoys in 1997 - 2002. The Delft3D model was calibrated and verified using tide tables from 10 tide gages of Hydrographics Department, Thai Navy in 2006 – 2016, water level data from Bangkok Bar station of Port Authority of Thailand in 2013 and current data from JICA at the mouth of Chao Phraya. The results from wave and current model found that tidal was the major effect on the circulation pattern in the Gulf of Thailand. However, some shallow water areas such as Ko Sichang station where the circulation is influenced by both tidal and wind.The oil spill model was calibrated using satellite image from GISTDA when the serious event of oil spill occurred near Ko Samet on 27 July 2013. From the model study, it found that the direction of oil spill movement corresponded to the direction of the wind. Oil moved off the coast of Rayong during the northeast monsoon, whereas oil moved toward to the coast of Rayong such as Maptaphut and Khao Leam Ya - Mu Ko Samet National Park during the monsoon transitions and the southwest monsoon. The position and time that the oil moving along the shoreline depend on the wind speed and direction. In May, there is a risk that oil spill will hit the Rayong coast the fastest in the year. It should have a special surveillance.
