The Gulf of Thailand, formerly the Gulf of Siam, is a shallow
inlet in the western part of the South China and Eastern
Archipelagic Seas, a marginal body of water in the western Pacific
Ocean. The gulf is around 800 km (497 mi) long and up to
560 km (348 mi) wide, has a surface area of 320,000 km2
(123,553 sq mi) and is surrounded on the north, west and
southwest by Thailand, on the northeast by
Cambodia and Vietnam. The
South China Sea
South China Sea is to the southeast.
2.1 Seabed morphology
3.2 Water quality
3.4 Coastal erosion
5 Territorial disputes
6 See also
8 External links
The modern Thai name of the gulf is Ao Thai (Thai:
อ่าวไทย, [ʔàːw tʰāj] ( listen),
"Thai Gulf") and "Gulf of Thailand" has been adopted as the official
name of the body by the International Hydrographic
Organization.[when?] Its name in Malay and Khmer continues to be
the "Gulf of Siam", Teluk Siam and Khmer:
ឈូងសមុទ្រសៀម, Chhoung Samut Siem,
respectively. In Thai, the gulf is historically known as Ao Sayam
(Thai: อ่าวสยาม). In Vietnamese it is known as
Vịnh Thái Lan.
It is generally identified with the Great Gulf (Latin: Magnus Sinus)
known to Greek, Roman, Arab, Persian, and Renaissance cartographers
before the influx of
Portuguese explorers removed the phantom Dragon
Tail peninsula from European world maps in the 16th century.
Map showing the location of the gulf
The Gulf of
Thailand is bordered by Cambodia, Thailand, and Vietnam.
It occupies a seabed area of 304,000 km2 from 6° N to 13°30' N
latitude and 99°E to 104° E longitude.:250 The northern tip of
the gulf is the
Bay of Bangkok
Bay of Bangkok at the mouth of the Chao Phraya River.
The southern boundary of the gulf is defined by a line from Cape Bai
Bung in southern
Vietnam (just south of the mouth of the Mekong River)
to the city of
Kota Bharu on the Malaysian coast.
The gulf is relatively shallow: its mean depth is 58 metres
(190 ft) and the maximum depth is only 85 metres
(279 ft).:250 This makes water exchange slow, and the strong
water inflow from the rivers reduce the level of salinity in the gulf
(3.05–3.25 percent) and enriches the sediments. Only at greater
depths does water with a higher salinity (3.4 percent) flow into the
gulf from the South China Sea. It fills the central depression below a
depth of 50 metres (160 ft). 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 flowing into
Bandon Bay in the southwest
of the gulf.
International Hydrographic Organization
International Hydrographic Organization defines the southern limit
of the gulf as "[a] line running from the Western extreme of Cambodia
or Camau Point (8°36'N) 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)".
The seabed morphology in the central depression of the gulf is
characterised by the presence of elongated mounds and ridges arranged
parallel to the axis of the basin. This morphology, widespread within
the gulf in water depths exceeding 50 m, covers an area of tens of
thousands of square kilometres.
It reflects an interaction between sediment dewatering and the
erosional activity of the present-day bottom currents. The sediment
dewatering and fluid seepage result in the formation of numerous small
pits and pockmarks. The long-term erosion imposed by currents of
stable orientation modifies pockmarks into long runnels and
depressions, and ultimately leads to the formation of the large fields
of elongated mounds and ridges, as well as the residual outliers of
un-eroded mud and clay sheets.
Bay of Bangkok
Bay of Kompong Som (Chhak Kompong Som)
Veal Rinh Bay
Chhak Koh Kong
Vinh Tuan Ven
Vinh Ba Hon
Vinh Hon Chong
See also: List of islands of Thailand, List of islands of Cambodia,
and List of islands of Vietnam
The larger islands in the gulf include:
Ko Pha Ngan
Ko Samae San
Koh Kong (island)
There are 75,590 rai of coral reef in the gulf, of which five percent
are considered to be in fertile condition. In 2010 severe coral
bleaching occurred at most reef sites in the country. Bleaching of
reefs in the
Andaman Sea was more severe and extensive than that in
the Gulf of Thailand. In 2016, coral bleaching was detected at Ko
Thalu and Ko Lueam in
Prachuap Khiri Khan Province
Prachuap Khiri Khan Province for the first
Coastal water monitoring results in 2015 from 202 sampling locations,
collected twice annually, indicate that no Thai coastal waters were
found to be in excellent condition. Sixteen percent of coastal water
was of good quality, 72 percent was of fair quality, 9 percent was of
poor quality and 3 percent was of very poor quality. The quality of
all coastal waters exhibited similar percentages — most were of fair
quality — except for the Inner Gulf of Thailand, where the coastal
water was poor to very poor. In comparison to coastal water quality as
measured in 2014, water quality has deteriorated.:52 Some gulf
waters off Chachoengsao Province, Samut Sakhon Province, Samut Prakan
Province, Bangkok, Rayong Province, Chonburi Province, Phetchaburi
Province, Prachuap Khiri Khan Province, and
Surat Thani Province
Surat Thani Province were
judged to have coastal waters in "poor" or "very poor"
condition.:54 Songkhla was the only province on the gulf with
coastal water rated "good" quality.:56
Of Thailand's total marine catch, 41 percent is caught in the Gulf of
Thailand and 19 percent in the Andaman Sea. Forty percent is caught in
waters outside Thailand's EEZ.
Thailand has 1,660 kilometres of coastline bordering the gulf. "Severe
erosion", more than five metres of coastline loss per year, afflicts
670 kilometres of that total. At least some of the erosion is
attributable to the clearing of mangrove forests to make way for
Eden's whale feeds in the gulf
Eden's whale off Bang Tapun.
The gulf's many coral reefs have made it attractive to divers. The
tropical warmth of the water attracts many tourists. Some of the most
important tourist destinations in the Gulf of
Thailand are the islands
Ko Samui and
Ko Pha Ngan
Ko Pha Ngan in Surat Thani Province,
Cha-am in Phetchaburi Province,
Hua Hin in Prachuap
Khiri Khan Province, and
Ko Samet in Rayong Province.
In recent years, the bay has become known for its whale watching
activities, targeting the endemic, critically endangered populations
of cetaceans (Eden's whales, newly described Omura's whales,[citation
needed] Chinese white dolphins, and Irrawaddy dolphins showing unique
feeding behaviors), and dugongs. It was first classified
by Müller in 1776 as Trichechus dugon. Presence of a critically
endangered Hawksbill sea turtle, a rare species in Thai waters, was
confirmed during whale watching expeditions in January, 2016.
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. A long-standing dispute between
Vietnam in the Gulf of
Thailand concerns mainly the island of Phú
Quốc or Koh Tral in Khmer, which is off the Cambodian coast.
Cambodia also claims 48,000 square kilometres (19,000 sq mi)
of shelf area.
Southeast Asia portal
^ "Marine Gazetteer browser". Marineregions org. Retrieved June 6,
^ "Thailand, Gulf of". Oxford University Press. Retrieved June 6,
^ "Marine Gazetteer Placedetails - Gulf of Thailand". Marineregions
org. Retrieved June 6, 2016.
^ "Gulf of Thailand". Deepseawaters.com. Retrieved June 7, 2016.
^ a b "Limits of Oceans and Seas" (PDF) (3 ed.). International
Hydrographic Organization. 1953. p. 23. Retrieved 7 February
พ.ศ. 2470 [A report on the royal travel through the Gulf of Siam,
Royal Thai Government Gazette
Royal Thai Government Gazette (in Thai). Bangkok: Cabinet
Secretariat. 88 (D): 44. 1927-05-22. Retrieved 2014-03-08.
^ a b Khongchai, Narongsak; Vibunpant, Somchai; Eiamsa-ard, Monton;
Supongpan, Mala. "Preliminary Analysis of Demersal Fish Assemblages in
Coastal Waters of the Gulf of Thailand" (PDF). Worldfish. Archived
from the original (PDF) on 19 February 2015. Retrieved 19 Feb
^ a b Puchala, R. (2014), Morphology and origin of modern seabed
features in the central basin of the Gulf of Thailand,
doi:10.13140/RG.2.1.3891.0808 (inactive 2017-01-19)
^ a b Oceans in the Balance,
Thailand in Focus (PDF). Bangkok:
Southeast Asia (Thailand). c. 2012. Retrieved 11 July
^ Wipatayotin, Apinya (2016-04-04). "Rising sea temps bring coral
bleaching to Gulf". Bangkok Post. Retrieved 4 April 2016.
^ a b c
Thailand State of Pollution Report 2015 (PDF). Bangkok:
Pollution Control Department, Ministry of Natural Resources and
Environment (Thailand). 2016. ISBN 978-616-316-327-1. Retrieved 5
^ Wipatayotin, Apinya (10 December 2017). "Shoring up defences".
Bangkok Post Spectrum. 10 (50). Retrieved 10 December 2017.
^ "Dugongs and seagrass in Thailand: Present status and future
challenges" (PDF). Phuket Marine Biological Center and Department of
Marine and Coastal Resources. pp. 41–50. Retrieved June 7,
^ "Conservation of the
Dugong Dugon) on the Eastern Coast of
the Gulf of Thailand" (PDF).
Ocean Park Conservation Foundation
Aberdeen, Hong Kong & Project Aware, Australia. May 1, 2004.
Retrieved June 7, 2016.
^ Marsh, H. et al. (2002). Dugong: status reports and action plans for
countries and territories Archived 2007-05-08 at the Wayback Machine..
Dugong dugon. The Paleobiology Database. Retrieved on 22 July 2007.
^ "Wild Encounter Thailand". www.facebook.com. Retrieved 16 March
^ "Defining areas for joint development in disputed waters -
Thailand p. 13". University of Wollongong. Retrieved June
^ Prescott, J. R. V. (1978). Boundaries and Frontiers. Rowman and
Littlefield. ISBN 0847660869.
^ Paul Ganster & David E. Lorey, Borders and border politics in a
^ Schofield, Clive (2008). "Maritime Claims, Conflicts and Cooperation
in the Gulf of Thailand".
Ocean Yearbook Online. Koninklijke Brill NV.
22: 75. doi:10.1163/221160008x00064. Retrieved June 7, 2016.
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Maritime boundary delimitation in the gulf of
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Clive Howard (1999)
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