The bloom of green Noctiluca scintillans, a mixotrophic dinoflagellate, has been recognized as an increasingly important ecological phenomenon in the Gulf of Thailand, where coastal ecosystems are subject to eutrophication and climate variability. The past few years have seen the occurrence of blooms consisting of green Noctiluca extending from the upper Gulf down to the lower Gulf of Thailand, significantly increasing in intensity, raising concerns about the eventual ecological impact and change in phytoplankton community structure. However, little is known about the long-term variability and environmental drivers of these events due to the lack of continuous observations for the period of several decades. In this research, satellite measurements of ocean color over 20 years (2003-2026) were employed, together with a regionally developed satellite algal bloom detection algorithm, to create a consistent time series of the occurrence and distribution of the green Noctiluca blooms. The interannual variability, seasonal features, and long-term trends were quantified and analyzed, while their correlations with environmental parameters, including sea surface temperature, precipitation rate, river discharges, and wind regime, were also studied. Satellite observations indicate a significant interannual variability of the blooms of green Noctiluca, including their changes in frequency of occurrence, distribution area, and seasonal occurrence over the last two decades. This study provides the first long-term satellite-based assessment of green Noctiluca bloom dynamics in the Gulf of Thailand, improving our understanding of long-term ecosystem change and supporting future assessments of ecosystem resilience under increasing climatic and anthropogenic pressures.