Boonyod Maklai, mayor of Tambon Haad Chao Samran in Muang Phetchaburi, led the outing on Kor Kai Bay and off Laem Phak Bia Cave.
Boonyod said the whales fed on plentiful plankton in Kor Kai Bay and also off the coasts of Samut Songkram, Samut Sakhon and Chachoengsao from October to December each year.
His tambon administrative organisation has trained tour-boat skippers to keep at the proper distance for observing the whales, and they must ensure that all passengers are wearing life-vests.