This is a part of our Cambodia forums to chat about anything Cambodia-related. This discussion forum is at the top of our site because it's usually the busiest part of the expat community chatter with random topics on just about everything, including expat life, Khmer politics, Cambodian blogs we have or have come across, or whatever else our members want to discuss. Whether you're an expatriate, tourist, Cambodian or random traveler just passing through South East Asia, you are welcome to talk about anything or start new topics yourselves.
Rode around the neighborhood and look for signs of land for sale or even just ask around. It's quite hard to establish a real market price here, as people put properties for sale at all sorts of ridiculous prices. The cheapest or near cheapest you see is usually the actual going price when it comes to land that actually sells. The rest is people "fishing". So go around and average it out. You might see stuff from say, for example, 30-90$/sqm, then 30-40 is likely the sellable price (taking other things into account of course: road quality/size, location etc).
As for finding a buyer, you can advertise with a sign, but if it's a booming area a real estate agent will likely steal it, or most of the callers will be real estate agents.
If you think the plot is excellent and it's something you really want then don't degrade yourself with bartering and pay whatever they ask for - in reason. There's good reason for this. By doing so you inflate all the local land values once word gets out what the land went for.