Mangrove ecosystems, one of most dynamic coastal habitats, are sensitive to sea level fluctuations and climate changes. In this research, mangrove environments are investigated and used to unravel the last 1500-year of mangrove dynamics, environmental history and anthropogenic activities in the upper and eastern Gulf of Thailand coast. Several palaeobotanical techniques are employed including pollen, charcoal, particle size and trace element analyses on at three contemporary mangrove locations, Samut Songkhram, Bangkok and Trat. The pollen record showed that mangroves dominated all three areas indicating these areas have been influenced by sea level and are thought to be a part of a palaeo-shoreline of the Gulf of Thailand from at least 450 CE. After 1250 CE, a lower sea level occurred until around 1700 CE. The palaeobotanical evidence suggests the replacement of mangroves by grasses at this time, and the upper Gulf of Thailand formed a young delta. There was a concomitant in pollen from cultivated plants suggesting possible agriculture practices around the upper shoreline during that period. After that, mangroves re-colonised illustrating the recent sea-level rise. In addition, increased charcoal, particle size and heavy metals were recorded suggesting intensive human activities occurring along the Gulf during the last centuries.