Though infrequent the Andaman coast is exposed to long period swells of up to 20+ seconds generated in the Southern and Indian Oceans. Swell tends to be small (2-4ft) in size coming from a SSW-SW direction but will also bend in nearer the coastline losing some size and energy in the process. The two images below show the narrow swell corridors for Phangnga and Ranong provinces. Phangnga's window is aproximately between 229-246 degrees, and Ranong's 223-239.
Notice how groundswells directed at Phangnga come in south of the Similan islands whereas groundswells hitting Ranong squeeze between the Surin and Similan islands offshore.
