This study analyses Holocene sediments from five boreholes and the Phanom Surin shipwreck site in the Lower Central Plain of Thailand to reconstruct lithostratigraphy and paleoenvironmental change. Six lithologic units and 15 ostracod species were identified, reflecting tidal–intertidal and prodelta settings. A fining-upward succession records a shift from Early–Middle Holocene tidal flats and channels to a Late Holocene prodelta system shaped by tidal and marine processes.