Pailin (Khmer: ប៉ៃលិន, Pailĭn [ˈpajlɨn]) is a province in western Cambodia at the northern edge of the Cardamom Mountains near the border of Thailand. This province is surrounded by Battambang province, and was officially carved out of Battambang to become a separate administrative division after the surrender of the Ieng Sary faction of the Khmer Rouge in 1996. Pailin is known to much of the world for having long been a stronghold of the Khmer Rouge, remaining under their control long after they were defeated in 1979 and serving from 1994 to 1998 as the capital of the Provisional Government of National Union and National Salvation of Cambodia. Within Cambodia, Pailin is known for its natural resources, namely precious gems and timber.

Once a part of the powerful Khmer Empire, Pailin was conquered in 1558 by the Burmese under Bayinnaung and later ruled by the Siamese (Thai) until 1907 and from 1941 to 1946 when it was returned to Cambodia. It was known to the Thai as "Phailin" (Thai: ไพลิน, Thai pronunciation: [pʰāj.lin]). There is still a vibrant border crossing point in Pailin. On 22 December 2008, King Norodom Sihamoni signed a Royal Decree that changed the municipalities of Kep, Pailin and Sihanoukville into provinces, as well as adjusting several provincial borders.

Pailin City (Krong Pailin) was founded under the Khmer Empire where it existed as an important trading centre. It continued its role as a centre of trade and commerce under French colonial rule which saw the establishment of French-operated stores and plantations. During the late 1800s, the area saw an influx of immigrants from Burma who became the Kula people. The Kula settled around Pailin and established structures whose architecture was based off the architecture of Burma.

In the early 1970s, Pailin was a prosperous town stemming from the extensive gem deposits in the surrounding countryside. Because of its resources, it was one of the first cities invaded by the Khmer Rouge when they began their major offensive against the Khmer Republic government. The city offered no resistance and the Khmer Rouge soldiers were greeted as liberators as they marched into town. At this point, the deposed prince Norodom Sihanouk had allied himself with the Khmer Rouge and most residents believed that they were fighting to restore him to power. It was not long though before most residents were rounded up for a forced march to the countryside to work in rice paddies. Those believed to have connections to the government were killed. The Khmer Rouge used proceeds from mining in the Pailin area to fund their offensive and later their government once they gained national power. When the invading People's Army of Vietnam ousted them from power, they retreated to Pailin, where many former Khmer Rouge leaders remain today. It was the capital of the Provisional Government of National Union and National Salvation of Cambodia.

Some leaders went into hiding in fear of punishment for their crimes, although other leaders lived openly in the province. As of September 2007, Pailin's remaining Khmer Rouge leaders were being rounded up to face justice by an international tribunal, including Khieu Samphan and Nuon Chea.

Since the war, Pailin suffered an economic decline and failures of local businesses. However, the now politically stable area is seeing a new wave of tourism focused on its ancient temples, natural forests and wildlife, and especially the precious gem market.

Until 2001, Pailin was part of Battambang Province, then elevated to city/municipal status, and then again to provincial status and thus became an autonomous zone of its own.

The current governor of Pailin province is Ban Sreymom, appointed by royal decree on 18 December 2020. Sreymom is a member of the ruling Cambodian People's Party and previously represented Pailin constituency in the National Assembly. She is the second woman in Cambodian history to serve as a provincial governor.

When Khmer Rouge forces surrendered in the late 1990s, the Cambodian government headed by Hun Sen allowed former members to manage modern-day Pailin as a special administrative area to facilitate and maintain peace.

The province is divided into 1 municipality and 1 district, further divided into 8 communes.

Map	#	ISO code	Name	Khmer	Population	Subdivisions
	— Divisions —
		24-02	Sala Krau	សាលាក្រៅ	7,106	4 sangkat
		24-01	Pailin	ប៉ែលិន	37,393	4 sangkat

According to the National Institute of Statistics of the Ministry of Planning, the total population of the province in 2013 was 65,792 which grew to 67,166 in 2014. In the latest census conducted in 2019, the province's population was at 71,600. Between 1998 and 2008, Pailin had the largest annual growth rate of any province in Cambodia at 11.2%. It then became one of the smallest, with annual growth rate between 2008 and 2019 being at 0.1%.

The surrounding area was rich in a variety of gemstones which were mined almost clean to support the Khmer Rouge. They also logged the area extensively, creating great environmental damage. Now all you can find is low-quality, cheap, hand-faceted gemstones at the market in downtown Pailin.

Traders in Pailin will accept Cambodian riels, US dollars, and Thai baht; US dollars are preferred.

Unlike in most of Cambodia, Pailin is composed primarily of uplands where little rice is grown. This makes it very difficult for farmers to rely on subsistence agriculture. Crop failures trigger foraging, increasing the number of land mine accidents. Many farmers produce non-traditional crops for the markets, including sesame, mung and soya. In 2003-04 it produced 17,204 tons of maize, the second-highest production in the country.

According to the Mekong Institute in 2013, longans were the third most important crop in Pailin province behind cassavas and maize. In Pailin, they are usually harvested between August and December. The most common variety of longans farmed are Pailin longans, which are farmed primarily in Battambang, Banteay Meanchey and Pailin provinces. In 2012, longan planting areas in the province occupied 425 hectares (1,050 acres) and produced 1,000 tons, increasing to almost 4,000 hectares (9,900 acres) in 2024. Around 60% of Pailin longans produced in 2012 was supplied to domestic market while 40% was sold to Thai buyers. From January to November 2022, farmers harvested 6,900 tonnes of longan, with 500 tonnes being exported to China. Longans have only been approved for export directly to China since 27 October 2022. Chinese demand for Pailin longans then rose, with China becoming the largest export market in the first half of 2023.

Vouch Thuch (born 1983) is believed to be the first longan wine maker in Cambodia and operates the local Pailin Longan Wine Handicraft in the province. Arriving in Pailin in 2000, he saw that longan lacked the market and started the longan wine business in 2008 trademarked as 'Palowin'. He replicated this with mangoes and mango wine. In July 2022, his winery was visited by U.S ambassador to Cambodia W. Patrick Murphey.

Wat Phnom Yat

Built by Shan migrants from Myanmar in 1922, the Wat Phnom Yat is a holy place for worship in the heart of Pailin. It includes an old pagoda, similar to the Kola pagoda.

Wat Rattanak Sophoan

At the foot of Phnom Yat is another pagoda, the Wat Rattanak Sophoan, "a Burmese style pagoda more than 570 years of age". On the walls of the enclosure surrounding the pagoda is a bas-relief depicting the Hindu saga of the churning of the Ocean of Milk.

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Pailin's culture is distinctly different from most of Khmer culture. Before the Khmer Rouge period, Pailin's culture was predominantly Shan Burmese, and has much in common with that of the country of Thailand and Burma. This affinity is shown in the region's cuisine, dress, temple architecture, festivals and arts. The people of Pailin were predominantly Kola. The Kola people originally migrated from Burma beginning in 1876 (note: Khmer people called the Burmese people, "Kola" or "Pumea"). Another wave of migrants, the Shan (one of the many ethnic minorities of Burma) arrived from Burma in the 1920s. The "Kola" or Burmese immigrants of Pailin are known for their work in the precious gem business, which likely is what attracted them to Pailin. Pailin was synonymous with the Mogok region of Burma, where similar precious gemstones were mined. According to people who are in the gem business, gemstones of Pailin are comparable to the gemstones from the Mogok region in Burma; thus, Khmer people believed the Kola or immigrants from Burma were from the Mogok region of Burma).

There are several dialects spoken locally including Khmer, Shan and Kola. The local Khmer dialect shows influence in tone and pronunciation from the Burmese languages as well as Kham Muang and Mon language.

In Pailin, there are a few different kinds of foods. Kola's food is distinct from Burma's Cuisine as well. The most popular Burmese style one is Kola noodles (មីកុឡា, mee kola) which is a vegetarian noodle dish made from thin rice stick noodles, steamed and cooked with soy sauce and garlic chive, sometimes mixed with some meats and small lobster. Other dishes include Tom yum from Thailand and Mon banana pudding of Burma. These have all spread to other parts of Thailand and Cambodia, but normally in versions that are flavored more sweetly than the Pailin version, especially in Phnom Penh.

The Traditional clothes of Pailin is Longyi, also known as Sarong. The cloth is often sewn into a cylindrical shape. It is worn around the waist, running to the feet. It is held in place by folding fabric over, without a knot. It is also sometimes folded up to the knee for comfort. These traditional "longyi" have about 2 meters of in length of a swan. The cloth is made of cotton and sometimes from silk. Kola men wear ankle-length patterns of checks, plaids or stripes "Longyi" in any kinds of color. The Men always wear their white eingyi shirt which has a mandarin collar and sometimes also wear a traditional jacket called taik-pon over their eingy. It has white, grey, black or terracotta colors. They put the gaung baung turban on their head and on their feet wear simple rubber or velvet slippers.

For Kola women's calf-length longyi are in solid colors, flower prints and many kinds of designs. They often have a red-based color, with partial stripes or very small checks similar to what Mon wear. They also often have horizontal or vertical stripes at the middle part. Royalty traditionally wore a long dress called "thin-dai" decorated by many threads. It was always worn by a lord's daughter and the king of the province's lady. The Women wear a beautiful blouse and a lovely shirt which is known as eingyi. The shirt is decorated with several colors and many pieces of silver. The shirt also has horizontal or vertical stripes at the middle part in some beauty color. Kola women tie a traditional shawl on their eingyi as well as they put the shawl on their shoulders. Women tie a lovely band on their head and wear beautiful flowers in their hair, allowing their hair to drop as a ponytail above their shoulders. They sometimes take a traditional umbrella made from bamboo with them. The footwear is simple slippers of leather or velvet called Hnyat-phanat.

All of these costumes were shiny with bright colors during celebrations. The clothing is very similar to what is worn by the Shan in Burma.

The houses in Pailin are built from wood, about 8 cm to 1 meter includes a wide door and in the middle of the house, there are the hermitages of Buddha and another spirit house. The Kola People are fond of planting roses in front of their homes.

Pailin and Cambodia, in general, was extensively mined during the three decades of war and remains home to numerous land mines and unexploded ordnance. People are cautioned to stay on marked roads. De-mining is ongoing with UN help, which brings in some of the few foreigners that the locals encounter.

Interestingly, resistance to Malaria drugs is surprisingly high in Pailin. Resistance first appeared in Pailin on the Cambodian-Thai border and then spread to Africa by the early 1980s. A second and third wave of resistance to a new set of malaria drugs occurred since. The local strain of malaria parasites may have some special properties, or the ecology of the region may have features that boost the rise of resistance.

• Rady Mom, US state representative in Massachusetts.

• The Cambodian Ministry of Tourism's website for the city of Pailin