Koh Kong is the mainland town right next to its namesake Koh Kong Island, just a short boat ride away. The town itself has doesn't have much to offer, but it does service travellers well for 3 things; visa runs from Thailand; a launch pad to the lovely Koh Kong Island and to the wilderness of the Cardamom Mountains rain-forest. Thanks to the completion of National Route 48, Koh Rong is now well connected to Phnom Penh and Sihanoukville, so you can make this a stop en route between Thailand and Southern Cambodia.
Unless you are passing through going to or from Thailand, Koh Kong isn’t somewhere you’d head to especially. With its proximity to the Thai border (just 8km), Koh Kong town established itself as a Wild West style town attracting some illegal activity. This includes illegal logging and animal trafficking.
The town seems to have got a bit of a boost from this with more 'eco-tours' into the surrounding mountains popping up. The term 'eco' is used loosely here, and most are just tours into the surrounding wildlife. Be sure to ask how their 'eco-tour' contributes to the surrounding are conservation. TIP - Remember this area is surrounded by rainforest and receives much higher rainfall than other regions of Cambodia. Be sure to have something to protect electronics from a sudden downpour!
If you are going to visit Koh Kong Island or visit the Cardamon Mountains, you need at least one full day here, meaning two or more nights.