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Gulf of Thailand

Gulf of Thailand

Located in the western Pacific Ocean, the Gulf of Thailand is a shallow entrance to the South China Sea. The nations of Thailand, Cambodia, and Vietnam encircle it. Formerly known as the Gulf of Siam, the Gulf is now referred to as Ao Thai (literally, “Thai Gulf”) in the modern Thai language.

Where is the Gulf of Thailand?

The Indochinese Peninsula’s southern portion and the Malay Peninsula’s northern part are separated by the Gulf of Thailand. Thailand borders the Gulf on three sides: the north, west, and southwest; the northeast is occupied by Cambodia and the southern region of Vietnam. The South China Sea is located southeast of the Gulf, while the Bay of Bangkok is located at its northern boundary.


The Gulf of Thailand has a maximum width of 560 km, a maximum length of around 800 km, and a total area of 320,000 km2. The Gulf is relatively shallow, with a maximum depth of 85 meters and an average depth of 58 meters. The Chao Phraya River and its tributaries, the Bang Pakong, the Tha Chin, and the Mae Klong rivers, are just a few prominent rivers that discharge waters and sediments into the Gulf of Thailand. 

The Gulf of Thailand is also the destination of the Mekong, Nakhon Chai Si, and Tapi Rivers. The low salinity of the Gulf is due to the significant intake of water from these rivers and the slow exchange of water with the South China Sea.

In the Gulf of Thailand, several bays may be found on the coastlines of Thailand, Cambodia, and Vietnam. These include the Thai bays of Ao Manao, Bangkok, Prachuap, and Sattahip; the Cambodian bays of Chhak Koh Kong, Kompong Som, Kep, and Veal Ring; and the Vietnamese bays of Vinh Ba Hon, Vinh Hon Chong, and Vinh Tuan Ven.

Ko Chang, Ko Khram, Koh Kong, Ko Pha Ngan, Ko Samui, Ko Samae San, Ko Tao, and other notable major islands can be found in the Gulf of Thailand. The Gulf of Thailand’s Prachuap Bay is home to the islands of Ko Rom, Ko La, Ko Lak, and Ko Raet. On the eastern side of the Gulf, Ko Chang is located not far from the border between Thailand and Cambodia. In the Gulf of Thailand, Koh Kong is the largest island belonging to Cambodia. The tiny Passe de Lămdăm divides this island from the mainland. Ph Quoc Island is the largest island in Vietnam and is located in the Gulf of Thailand, with a total area of 574 km2.


There are 121 km2 of coral reefs in the Gulf of Thailand. However, only 5% of that area is thought to be in a fruitful state. In 2010, the majority of the Gulf’s reefs underwent significant bleaching. In Thailand’s Prachuap Khiri Khan Province, coral reef bleaching was first noticed in 2016. Scientists have shown that coral bleaching starts to happen when the ocean temperature rises above 30 °C for longer than three weeks. Since Ko Thalu and Ko Lueam have had water temperatures over 32 °C for protracted periods, it has been calculated that 5 to 10% of the coral reefs in the Prachuap region have already bleached.

Some of the notable marine species that are found in the Gulf of Thailand are batfish, porcupine fish, long-finned bannerfish, triggerfish, jellyfish, hermit crabs, sea cucumbers, yellowtail barracudas, blue-spotted stingrays, hawksbill turtles, and different species of cetaceans like Chinese white and Irrawaddy dolphins, Omura’s and Eden’s whales, and dugongs.


Several fish with significant commercial value can be caught in the shallow waters off the Gulf of Mexico’s coast. Bangkok, Chanthaburi, Pattani, Pak Phanang, and Songkhla in Thailand; Kep, Kâmpôt, and Réam in Cambodia; and Rach Gia in Vietnam are some of the significant harbors that are situated along the Gulf. The islands of Ko Samet, Ko Samui, and Ko Pha Ngan are among the well-known tourist sites in the Gulf of Thailand, along with Pattaya, Hua Hin, Cha-am, and Hua Hin.

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