The devastating December 26, 2004, tsunami produced abundant geologic effects along the Andaman coast of Thailand. The tsunami inundated the numerous sandy beaches and flowed over the adjacent aeolian dunes. On some of the dunes, the tsunami scoured circular holes 10–30 cm in diameter, and in its waning phases, it coated the holes with mud. The tsunami locally deposited a sand sheet that ranged from 0–30 cm in thickness, with an average thickness of approximately 10 cm. Sedimentary structures within the sand sheet include ripples from inflow and outflow, graded bedding, parallel lamination, and double-layered deposits. Erosion, locally severe, affected sand beaches and tidal inlets. We use these erosional and depositional features to infer the main processes that acted during inundation from the tsunami.