The Gulf of Thailand is a shallow inlet located in the western part of the South China Sea. Also referred to as the Gulf of Siam, the gulf is a marginal body of water within the western part of the Pacific Ocean. The Gulf of Thailand has a length of 497 mi, a width of 348 mi, and covers a total area of 123,553 sq mi. Three countries have coastline along the Gulf of Thailand: Thailand, Cambodia, and Vietnam. Thailand is located to the north, west, and southwest of the gulf, while both Cambodia and Vietnam are located to the northeast. Additionally, the South China Sea is located southeast of the Gulf of Thailand.
The gulf features 75,590 units of coral reef, called rai, although only 5% are believed to be fertile. As of 2010, the coral reef on the Gulf of Thailand had experienced bleaching, which was a similar phenomenon observed in the Andaman Sea. Coral bleaching was detected in Thailand’s Prachuap Khiri Khan Province for the first time in 2016. Scientists discovered that when the temperature of seawater goes above 30 °C for a period of at least three weeks, coral bleaching begins to occur. The water temperatures at Ko Lueam and Ko Thalu in Prachuap have remained at 32°C for extended periods, and therefore between 5% and 10% of coral reef in the region are now bleached.
Prachuap Bay is located on the western side of the Gulf of Thailand, off the town of Prachuap Khiri Khan. The bay opens up towards the east, and is bound by stiff limestone outcrops that form a peninsula to the north. There are four islands located in Prachuap Bay: Ko Lak; Ko La; Ko Rom, which is located near the southern part of the bay's mouth; and Ko Raet, which is located further offshore. The island of Ko Lak has been the historical center of administration of Prachuap Khiri Khan Province, and its silhouette is on the provincial seal.
Ko Chang Island
Ko Chang, which is also referred to as Chang Island, falls within the administration of Thailand's Trat Province. The island is located on the eastern seaboard, about 192 miles from the city of Bangkok, and is close to the Thailand-Cambodia border. The island of Ko Chang occupies an area of 82 sq mi, while the administrative district of Ko Chang, in which the island is located, covers an area of 161 sq mi. The name Ko Chang means "Elephant Island" in the Thai language, and refers to the fact that the headland resembles the shape of an elephant. Although elephants can be found on the island, they are not indigenous. The Royal Thai Navy fought the Vichy French naval forces on the island of Ko Chang in 1941, which resulted in a decisive French victory. Each year in late January, Ko Chang Yutthanawi Day is held to commemorate the Royal Thai Navy's battle against the French colonialists.
Koh Kong is an island in the Gulf of Thailand that is located in the coastal waters of Cambodia. The island, which is the largest in Cambodia, is approximately six mi south of the town of Koh Kong, and falls within Koh Kong Province. The island of Koh Kong has a length of 12 miles, running north to south, an average width of 4 miles from west to east, and encompasses an area of 39 sq mi. The island is separated from mainland Cambodia by the Passe de Lămdăm strait, which is 1,640 ft wide. The southern end of the island is about 2 mi from the mainland coast, and the narrow strait leading to the Bay of Koh Kong covers an area of 52 square miles. Some of the marine animals that can be found around the island include sea turtles, whale sharks, dolphins, squids, shrimps, crabs, grouper fish, swordfish, wahoo fish, cobia fish, kingfish, barracuda, snapper fish, and parrotfish.
Thổ Chu Islands
Thổ Chu Islands are an archipelago in the Gulf of Thailand that are administered as part of Vietnam's Phú Quốc District, Kiên Giang Province. The archipelago consists of a group of eight islands that encompass a total area of 5.39 sq mi. Thổ Chu Island is the largest island in the Thổ Chu Islands, and was proposed to become a protected marine area in 1995. The Asian Development Bank (ADB) also proposed the creation of a marine protected area on the island that would cover an area of 86 sq mi, which was to include 4.6 sq mi of land and 81.9 sq mi of water. Thổ Chu Islands have historically been part of a disputed territory between Vietnam and Cambodia. The island became occupied by the Khmer Rouge in 1975, resulting in the abduction and death of about 500 civilians. Vietnamese forces recaptured the island on May 27th, 1975, and successfully defended against another Khmer Rouge attack on the island in 1977. More recently, Malaysia Airlines Flight 370 lost contact with the ground on March 8th, 2014 while flying over Thổ Chu Islands.