Furthermore, it is likely that mixing population between the Gulf of Thailand and the Andaman Sea is limited, due to the gentle current flowing westward from the South China Sea which effectually prevent eastward connectivity between the Gulf of Thailand and the Andaman Sea (Klangnurak et al., 2012). The northern part of the Andaman Sea, above Phuket province, have less influence by the South China Sea that flow through Malacca Straights than the southern part of the Andaman Sea (Satapoomin, 2007). These may act effectively to Ostreopsis populations from the two seas as revealed in several marine organisms in Thailand