It continued to be an important centre for commerce during French colonial control, where several French-owned businesses and plantations were established.

Meanwhile, Khmer Rouge forces increased engagements against the Vietnamese-backed State of Cambodia over control of Pailin City and surrounding ruby and sapphire mines.

[7] On 23 September, Defense Minister Tea Banh acknowledged the Khmer Rouge's capture of land around Pailin in the government's first admission of losing territory in the war.

For them to work on 1 cubic yard (0.76 m3), each miner required a license issued by the Khmer Rouge costing ฿‎6,000 ($240 USD in 1990).

The rubies were then traded to makeshift markets on the other side of the border in Bo Rai district in Thailand, earning the Khmer Rouge around a million dollars per month.

[10] According to Human Rights Watch, the Khmer Rouge established a re-education camp for civilian administrators near Pailin City in the early 1990s.

The loss of Pailin initiated King Sihanouk to propose peace talks between the government and Khmer Rouge, which failed.