The waste, which included plastic bags and water bottles as well as organic matter, was also seen floating in the sea off the popular beach on Saturday.
The incident is a natural phenomenon that occurs every year between October and the beginning of November, when monsoon winds blow southwestward from Chon Buri toward Prachuap Khiri Khan on the opposite side of the Gulf of Thailand.
Local people call it the lom wao, or "kite wind", said Hua Hin Mayor Nopporn Wutthikul.
As a result, the winds sweep a huge amount of waste under the sea at the mouth of the Gulf of Thailand from Chon Buri, Bangkok, Samut Sakhon and Samut Songkhram to the province’s shoreline.
This phenomenon usually lasts about one or two weeks and is well known among local people, he said.
Mr Nopporn said more than 100 municipal officials were busy clearing up the trash along the shoreline, especially at a spot beside the Centara Grand Beach Resort & Villas Hua Hin, where many people like to go swimming.
He also said tourists should be aware that the seawater quality would be poor during this period and they may encounter waste that could be harmful floating in the sea.