Koh Maphrao, Gulf of Thailand.

Gulf Of Thailand

The Gulf of Thailand is a shallow inlet of the South China Sea located in the western part of the Pacific Ocean. It is surrounded by the countries of Thailand, Cambodia, and Vietnam. The gulf was formerly known as the Gulf of Siam, and in the modern Thai language, the Gulf is referred to as Ao Thai (“Thai Gulf”).

Where Is The Gulf Of Thailand?

gULF OF Thailand map
Gulf of Thailand map

The Gulf of Thailand is positioned between the southwestern part of the Indochinese Peninsula and the northern part of the Malay Peninsula. The Gulf is surrounded by Thailand in the north, west, and southwest, and by Cambodia and the southern part of Vietnam in the northeast. The Bay of Bangkok is situated at the northern edge of the Gulf whereas the South China Sea is situated in its southeastern part.


Angthong National Marine Park, Thailand, Gulf of Thailand. 

The Gulf of Thailand covers a total area of 320,000 km2 and has a length of about 800 km and a maximum width of 560 km. The Gulf is relatively shallow and has a maximum depth of 85 m and an average depth of 58 m. Many notable rivers discharge their freshwater and sediments into the Gulf of Thailand which include the Chao Phraya River along with its distributaries the Bang Pakong, the Tha Chin, and the Mae Klong rivers. The Mekong, Nakhon Chai Si, and the Tapi Rivers also drain into the Gulf of Thailand. The strong inflow of waters from these rivers and the slow exchange of the gulf’s water with the South China Sea account for the low salinity of the Gulf of Thailand.

Several bays are located along the coasts of Thailand, Cambodia, and Vietnam in the Gulf of Thailand. These are the Ao Manao Bay, Bay of Bangkok, Prachuap Bay, and the Sattahip Bay in Thailand; the Chhak Koh Kong Bay, Bay of Kompong Som, the Kep Bay, and the Veal Rinh Bay in Cambodia; the Vinh Ba Hon, Vinh Hon Chong and the Vinh Tuan Ven bays in Vietnam.

Some of the significant large islands that are located in the Gulf of Thailand are Ko Chang, Ko Khram, Koh Kong, Ko Pha Ngan, Ko Samui, Ko Samae San, Ko Tao, etc. The islands of Ko Rom, Ko La, Ko Lak, and Ko Raet are situated in the Prachuap Bay of the Gulf of Thailand. Ko Chang is positioned close to the Thailand-Cambodia border on the eastern part of the Gulf. Koh Kong is the largest island of Cambodia in the Gulf of Thailand. This island is separated from the mainland by the narrow Passe de Lămdăm. Covering an area of 574 km2, Phú Quôc Island is the largest island of Vietnam that is situated in the Gulf of Thailand.


A whale in the Gulf of Thailand. 

The Gulf of Thailand features about 121 km2 of coral reef, of which only 5% is considered to be in fertile condition. Most of the gulf’s reefs experienced severe bleaching in 2010. The bleaching of coral reefs was first detected in Thailand’s Prachuap Khiri Khan Province in 2016. It has been determined by scientists that when the seawater temperature exceeds 30 °C for more than a period of three weeks, coral bleaching begins to occur. The water temperatures at Ko Thalu and Ko Lueam have experienced more than 32 °C for long periods and therefore it has been estimated that about 5 to 10% of coral reefs in the Prachuap region have already been 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.


Fishing boats in the Gulf of Thailand.

The shallow waters along the coastal areas of the gulf serve as important fishing grounds for several commercially important fish. Some of the major harbors that are located along the Gulf are Bangkok, Chanthaburi, Pattani, Pak Phanang, and Songkhla in Thailand; the ports of Kep, Kâmpôt, and Réam in Cambodia and the port of Rach Gia in Vietnam. The famous tourist destinations that are situated in the Gulf of Thailand are Pattaya, Hua Hin, Cha-am, and the islands of Ko Samet, Ko Samui, and Ko Pha Ngan.

Map of Thailand with the Gulf of Thailand.

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