Coastal carbonate boulders (CCBs) occur on Ko Larn island in the Bay of Bangkok.
CCBs >0.5 m in length are found at elevations up to 4 m above m.s.l.
Minimum flow velocities of 4.7 m/s and 7.1 m/s are needed to transport 50% and 100% of measured CCBs.
CCB deposits are signatures of past high-energy wave events.
Prehistorical typhoons may have impacted the Bay of Bangkok.