Abstract: Based on the LSC05 and WLE08 core samples obtained from the Chanthaburi coast of the Gulf of Thailand in 2017, the biogenic silica, total organic carbon, and AMS¹⁴ C dating were analyzed. High-resolution data including grain size and biogenic silica content were obtained to explore the changes of paleoproductivity in the Gulf of Thailand since 9 ka. Results show that the contents of biogenic silica in the samples were 0.41% ~1.56% (on average of 0.88%) for LSC05 and 0.60%~1.52% (on average of 1.11%) for WLE08, belonging to the low-value sea area of the South China Sea. This area was mainly affected by low supply of siliceous bones caused by the absence of upwelling in the study area, and the input dilution of regional inland-sourced materials. By comparing the biogenic silica content curve with the South Asian summer monsoon substitution index curve and the temperature anomaly curve in the South China Sea, we found that the high-value period of sea surface primary productivity corresponds to the period with high biogenic silica content, which might be due to the strong phased force of the summer monsoon. The organic carbon content curve confirmed the reconstruction results of paleoproductivity by biogenic silica. In addition, comparison between the biogenic silica content curve and the records of Greenland ice core, Dongge cave stalagmite, and Qunf cave in Oman stalagmite showed that the trend of paleoproductivity in the Gulf of Thailand was significantly correlated with the global environmental changes, reflecting the response of paleoenvironmental changes in the Gulf of Thailand to global environmental changes.