Just to clarify.
We were offered 1 rai on the "main road" of the wifes village for 100 000B a few months ago. Well actually we were first asked to loan the money to the family to buy it as it was supposedly very cheap, but that's a story for another thread.
Mostly cleared and suitable for construction, it was Prime Real Estate in downtown Baan Raveang as it was on the corner of the "highway" and the "main road", so everyone coming from Rattanaburi had to pass it coming into the village. They were apparently in need of money and the land was worth 180 - 200K because of it's location. Normally land in the village tucked away off of the main road sells for the same price they were asking, 100k per rai. I was still deciding if I was stupid enough to buy it when it sold within a week for the asking price.
There can be bargains to be had but I would strongly suggest that you wait for someone who really needs to sell, and therefore you can bargain from a position of power rather than advertise the fact that you want to buy land because then you will get people to see how gullible you are and how much you can pay.
Location is always very, very important and when this piece of land became available, every single family in the village wanted to buy it. There were frantic phone calls to family members throughout Thailand to see who could raise the money first.
Hope this helps the OP a little.