Southern Thailand is seismically active, with earthquakes and tsunami. The chief culprit is the Indian tectonic plate (carrying the Indian ocean & subcontinent) which, like a skidding truck, is barrelling northwards while spinning anti-clockwise. In this region it collides with the small Burma plate, which carries the Andaman Sea. When the plates grind past each other (a “slip-strike” collision), they cause earthquakes. But the Indian plate is also being subducted – forced beneath the Burma plate – which lifts the sea-bed, displaces the water, and sets off a tsunami. A most violent event occurred on 26 Dec 2004, when along 1000 miles of fault line the sea-bed was suddenly jacked up by several metres. Two hours later, tsunami hit the west coast of Thailand in three waves 20 min apart, and over 8000 people here were killed.
There was, and is, no effective local warning system, as (unlike the Pacific) major tsunamis in the Indian Ocean are seen as a once-in-a-century event: “Not since Krakatoa in 1883” is the stock refrain. But memory of the 2004 tragedy remains strong. Expect frantic fleeing from the coast if an earthquake is felt, with gridlock and traffic casualties. Your decision will be whether to rush out of the building before it collapses, or rush indoors to try and get above the third floor.
The Burma plate is in turn being shunted against the Sundah plate, which carries the Peninsula mainland and eastern sea. This movement is less violent, but this fault line lies right under the western coastline, so these earthquakes have more local impact and tsunami could strike immediately. Central and Northern Thailand are less quake-prone but the 2014 Mae Lao earthquake, centred on Chiang Rai, caused one death.