The green and stinking sea led to many tourists leaving the beach amid fears of skin irritation.
A tourist from Pathum Thani province complained that her family trip to celebrate the long Mother's Day holidays was ruined by the state of the sea. She said that she had to prevent her children from playing in the seawater.
Meanwhile, a retailer near the beach said the sea was dyed green as seaweeds and planktons were swept ashore due to the monsoon, confirming that it was a natural phenomenon.
The plankton surge seriously impacted tourism as many tourists fled the beach, he said, expecting the phenomenon to last around seven days.