It has evolved parallel to the construction of the Sihanoukville Autonomous Port, which commenced in 1955, as the country's gateway to direct and unrestricted international sea trade.

[9] Saom is derived from the Sanskrit word saumya, the original (Rig Vedic) meaning of which was Soma, the 'juice or sacrifice of the moon-god', but evolved into Pali 'moon', 'moonlike' 'name of Shiva'.

[13][14][15] The Chronicle of Samtec Cauva Vamn Juon, one of the 18th- and 19th-century Cambodian Royal Chronicles, briefly mentions the region as the country was split into three parts during a civil war from 1476 to 1485: "In 1479, Dhammaraja took on the throne at Chatomuk (Phnom Penh) and controlled the provinces of Samraong Tong, Thbong, Kompong Saom, Kampot up to the Bassak, Preah Trapeang, Kramuon Sah, Koh Slaket and Peam" (mouth of the Mekong).

[17] A Cambodian king of the late 18th century, Outey-Reachea III, allied with a Chinese pirate,[18] Mac-Thien-Tu, who had established an autonomous polity based in Ha Tien and controlled the maritime network in the eastern part of the Gulf of Thailand.

In 1757, Ha Tien acquired the ports of Kampot and Kompong Som as a reward for Mac's military support to the king of Cambodia.

French Résident Adhemard Leclère wrote: "Until 1840s, the Vietnamese governed Kampot and Péam [Mekong Delta], but Kompong Som belonged to Cambodia.

Foreign Secretary Lord Palmerston's agent John Crawfurd reported: "Cambodia was...the Keystone of our policy in these countries, - the King of that ancient Kingdom is ready to throw himself under the protection of any European nation...The Vietnamese were interfering with the trade at Kampot, and this would be the basis of an approach".

Palmerston concluded: "The trade at Kampot—one of the few remaining ports, could never be considerable, in consequence of the main entrance to the country, the Mekong, with all its feeders flowing into the Sea through the territory of Cochin China .

Here is a point where the wedge might be inserted, that would open the interior of the Indo-Chinese Peninsula to British Commerce, as the great River of the Cambodians traverses its entire length and even affords communication into the heart of Siam".

It started in Kampot and quickly spread to Veal Rinh, Kampong Seila, and Kompong Som, where the insurgents were led by a Chinese pirate named Quan-Khiem.

After the dissolution of French Indochina in 1954, Vietnam's steadily tightening control of the Mekong Delta required a solution to gain unrestricted access to the seas.

The events surrounding the Khmer Rouge's taking of the U.S. container ship SS Mayaguez and its crew on 12 May and the subsequent rescue operation by U.S. Marines played out on the waters of Koh Tang off the coast of Sihanoukville.

[26] After the fall of the Khmer Rouge regime in 1979 and the subsequent opening of the economy, the port of Sihanoukville resumed its importance in the country's development and recovery.

After the completion of certain elements of the infrastructure, the investor announced alterations of the original blueprints, as "Reapplying for permission will happen in 2014", according to the Council of the Development of Cambodia.

[34][35] On 26 May 2011, the Preah Sihanouk area joined the Paris-based club Les Plus Belles Baies Du Monde ('the most beautiful bays in the world').

To its northwest and at its center it rises up to 15 metres (49 ft) above sea level, whereas the land gently and steadily flattens towards extended coastal plains, marshlands and beaches in the south and southeast.

The Gulf of Thailand's shallow depths and the local climate are moderate in contrast to the South China Sea to the east and the Indian Ocean to the west.

[41] Established after the period of the French Protectorate, bourgeois colonial style quarters such as ones seen in Kampot, Siem Reap, or Phnom Penh do not exist.

May is the warmest month – although strongly influenced by the beginning of the wet season, as the area constitutes the easternmost fringe of the south-west monsoon.

Sihanoukville was established as an international marine gateway and as a result the local economy is largely defined by its deep water port and the nearby oil terminal.

Attached is a regularly modernized cargo storage and logistics facility which serves numerous shipping companies, freight forwarders, suppliers, and maintenance contractors.

[56][57] In 2023, it was reported that Sihanoukville had become a major centre for fraud factories, where thousands of human trafficking victims forced to work as "pig butchering" scammers after COVID-19 led to the closure of many of the city's casinos.

[68] Foreign investment in Cambodia has increased significantly since 2004 led by Asian investors from countries such as Malaysia, China, Korea, Thailand, and Vietnam.

[73] The primary destinations of Sihanoukville Autonomous Port are: Singapore, Hong Kong, Bangkok, Ho Chi Minh City, Shanghai, Laem Chabang, Yantian and Kaohsiung.

[88][89][90] The central long-distance bus station for all transport business operators[91] is on National Highway 4 in the city's north-east near the Autonomous Port.

It is near National Highway 4, around 500 metres (1,600 feet) from Ream beach atop a former mangrove lagoon, about 18 kilometres (11 miles) from Sihanoukville City.

[98] The "Southern line", constructed from 1960 to 1969 with a length of 264 km (164 mi), connects Sihanoukville Port Special Economic Zone with Phnom Penh.

[99] In addition to Khmer, ethnic groups like Vietnamese, Chinese, Cham, Thai, Korean, French, British, Europeans, Australians, and Americans live in the urban area.

At the same time, modern standard private clinics, including local and foreign service providers, are increasing in number[quantify] and competing with state-owned hospitals.

[110] Embassies and consular officials have issued cautionary statements about travel to Sihanoukville following gang disputes and several high-profile murders, rapes, and robberies as well as several unexplained deaths of foreigners.