The Gulf of Thailand is bordered by Cambodia, Thailand, and Vietnam, with the Bay of Bangkok and the mouth of the mighty Chao Phraya River at its northern tip. Renowned for its many coral reefs, more recently the bay has become known for whale watching.The most popular holiday destination in the Gulf is Koh Samui, and away from the luxury resorts and exclusive spas there's a lively nightlife scene, so it maintains a broad appeal for everyone and has a distinctively relaxed atmosphere that sets it apart from other Thai islands.