Abstract: Chonburi Province is located in the core area of the eastern Gulf of Thailand, and serves as a major industrial-port hub, crucial to regional socio-economic development. Employing the Maximum Spectral Index Composite (MSIC) algorithm, high-tide imagery from 1994–2024 was retrieved, and shoreline data was extracted via the Otsu method. The shorelines were classified into eight categories—bedrock, muddy, sandy, estuarine, biological, and artificial (aquaculture dikes, port shoreline, construction dikes) to facilitate subsequent analyses of erosion-accretion dynamics and typological transitions. Surface-sediment grain-size analyses were conducted on sand-dominant, anthropogenically active shorelines, and driving factors of shoreline evolution were identified. Between 1994 and 2024, Chonburi’s shoreline length first increased then declined, expanding overall from 175.52 km to 179.62 km. This reflects a structural shift characterized by contraction of natural shorelines and expansion of artificial ones. Severe erosion concentrates on sandy coasts, where sediments are predominantly silty with a unimodal distribution; erosion intensity follows a south ＞ central ＞ north gradient. The areas with intense erosion include four sandy coasts: Bang Saen Beach, Krathing Lai Beach, Pattaya Beach, and Phala Beach. The most extensive erosion occurred from 2014 to 2024, accounting for 43.32 % of the total. Both natural and anthropogenic forces drive shoreline change: sea-level rise, reduced fluvial sediment supply, and the mobility of silty shores exacerbate erosion; recreational use and infrastructure on sandy beaches destabilize them; reclamation directly converts sea to land; and breakwaters erected for port expansion alter hydrodynamic conditions, attenuate wave energy, and promote sediment deposition. Collectively, these human interventions facilitate seaward shoreline expansion in Chonburi Province.