Gulf of Thailand

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Gulf of Thailand
Gulf of Thailand.svg
Gulf of Thailand
Location Southeast Asia
Type Gulf
Primary inflows South China Sea
Surface area 320,000 km2 (120,000 sq mi)
Average depth 45 m (148 ft)
Max. depth 80 m (260 ft)
Map showing the location of the gulf

The Gulf of Thailand (Thai: อ่าวไทย, RTGS: Ao Thai, Thai pronunciation: [ʔàːw tʰaj]), formerly called the Gulf of Siam (Thai: อ่าวสยาม; RTGS: Ao Sayam),[1] is a shallow arm of the South China Sea.[2]

It is also known to the Malays as Teluk Siam and to the Khmers as Boeung Tonle Siem, both literally meaning the Gulf of Siam.


The Gulf of Thailand is bordered by Cambodia, Thailand and Vietnam. The northern tip of the gulf is the Bay of Bangkok at the mouth of the Chao Phraya River. The gulf covers roughly 320,000 km². The boundary of the gulf is defined by the line from Cape Bai Bung in southern Vietnam (just south of the mouth of the Mekong river) to the city Kota Bharu on the Malaysian coast. At the height of the last ice age the Gulf of Thailand did not exist, due to the lower sea level, the location being part of the Chao Phraya river valley.

The Gulf of Thailand is relatively shallow: its mean depth is 45 m and the maximum depth is only 80 m. This makes water exchange slow, and the strong water inflow from the rivers reduce the salinity in the Gulf (3.05–3.25%) and enrich the sediments. Only at the greater depths does water with a higher salinity (3.4%) flow into the gulf from the South China Sea. It fills the central depression below a depth of 50 m. The main rivers which empty into the gulf are the Chao Phraya, including its distributary Tha Chin River, the Mae Klong and Bang Pakong Rivers at the Bay of Bangkok, and to a lesser degree the Tapi River into Bandon Bay in the southwest of the gulf.

The International Hydrographic Organization defines the southern limit of the Gulf of Thailand as a line running from the Western extreme of Cambodia or Camau Point (8°36'N), a point which is actually in Vietnam, to the Northern extreme of the point on the East side of the estuary of the Kelantan River (6°14′N 102°15′E﻿ / ﻿6.233°N 102.250°E﻿ / 6.233; 102.250).[3]


The Gulf of Thailand harbours many coral reefs that are suitable locations for diving resorts. The tropical warmth of the water attracts many tourists. Some of the most important tourist destinations in the Gulf of Thailand are the islands of Ko Samui and Ko Pha Ngan in Surat Thani Province, Pattaya in Chonburi Province, Cha-Am in Phetchaburi Province, Hua Hin in Prachuap Khiri Khan Province, Ko Samet in Rayong Province, and Ko Chang in Trat Province

Ko Tao is a center of the diving tourism.

Territorial disputes[edit]

The area between Malaysia, Thailand, Cambodia and Vietnam is subject to several territorial disputes. Malaysia and Thailand have chosen to jointly develop the disputed areas, which include the islands of Ko Kra and Ko Losin.[citation needed] A long-standing dispute between Cambodia and Vietnam in the Gulf of Siam concerns mainly the island of Phú Quốc or Koh Tral in Khmer, which is located off the Cambodian coast.[4] Cambodia also claims 48,000 km2 of shelf area.[5]

See also[edit]


  1. ^ "ระยะทางเสด็จฯ ประพาสชายทะเลอ่าวสยาม พ.ศ. 2470" [A report on the royal travel through the Gulf of Siam, 1927] (pdf). Royal Thai Government Gazette (in Thai) (Bangkok: Cabinet Secretariat) 88 (D): 44. 1927-05-22. Retrieved 2014-03-08. 
  2. ^ Proceedings of the Royal Geographical Society
  4. ^ John Robert Victor Prescott, Boundaries and frontiers
