The Upper Gulf of Thailand is known for its population of Bryde’s whales (also known as Eden’s whales or Balaenoptera edeni). This is a remarkable species that can grow up to 11 to 12 metres in length and weigh up to 15 to 20 tonnes. The coastal ecosystem of the  Gulf of Thailand is enriched by the nutrients of four major rivers that empty into the Gulf: Mae Klong, Tha-Jeen, Chao Phraya, and Bang Pakong. The nutrients from these rivers are carried through mangroves and mudflats along the shore, contributing to the biodiversity of the Gulf waters, providing an abundance of food, such as schools of fish and copious plankton, for the whales. Today, the Gulf of Thailand is home to over 80 identified individual whales, including at least 15 pairs of cows and calves. They surface to “trap-feed” in the monsoon season, when the nutrition level in the water reaches its peak. An optimum time to observe whales in the Gulf is July through to the end of the year.

The Natural History Section of The Siam Society will lead a one-day whale-watching boat trip to the Upper Gulf of Thailand on Saturday, 8 August 2026. The trip will be led by Mr Visanu Euarchuakiati, Member of the Council and the Natural History Section of The Siam Society, in collaboration with the ecotourism company Wild Encounter Thailand. This study trip presents a unique opportunity to observe Bryde’s whales in their natural habitat; dolphins, porpoises, seabirds, and other marine species that feed on fish driven to the surface by the whales’ dynamic underwater movements may also be spotted. The observation will be conducted with strict considerations for wildlife and environmental conservation, with expert guidance from a Wild Encounter naturalist and whale-watching crew, offering insights into efforts to protect these remarkable mammals and their fragile ecosystem. Participation in the trip also supports a citizen science approach of whale exploration, where sighting data is shared with the Department of Marine and Coastal Resources’ Marine Endangered Species Unit.