Various antifouling biocides were surveyed in sediment and green mussels (Perna viridis) from the coastal area of Thailand. The concentrations of butyltin (MBT), dibutyltin (DBT), and tiributyltin (TBT) in sediment from Thailand were in the range of 1–293 μg kg⁻¹ dry wt., 1–368 μg kg⁻¹ dry wt., and 2–1246 μg kg⁻¹ dry wt., respectively. A higher concentration of TBT was observed in industrial areas, where many tankers and cargo ships sail and moor. Phenyltin (PT) compounds were not detected in most of the sampling sites. The concentrations of MBT, DBT, and TBT in green mussels from Thailand were in the range of 8–20 μg kg⁻¹ wet wt., 4–9 μg kg⁻¹ wet wt., and 4–45 μg kg⁻¹ wet wt., respectively. The concentration of TBT was high in an area where aquaculture practice is common. The detection frequencies of TPT were low. Representative booster biocides were surveyed in sediment. The detection frequencies of Sea Nine 211 were low (2/13). Furthermore, Sea Nine 211 concentrations in the detected samples were at values near the detection limit (0.051–0.094 μg kg⁻¹ dry wt.). Diuron was detected at the highest level among the booster biocides in the range of 0.07–25 μg kg⁻¹ dry wt. Irgarol 1051 was detected in the range of 0.03–3.2 μg kg⁻¹ dry wt., and concentrations of the degradation product’s M1 were 0.03–4.9 μg kg⁻¹ dry wt. Diuron and Irgarol 1051 showed higher concentrations in industrial areas and fishery sites, respectively. Diuron was only detected among green mussels in the range of <0.64–9.6 μg kg⁻¹ wet wt. The lower ratio of Diuron and Irgarol 1051 for TBT concentration suggests that TBT is still being used in Thailand.