The most common painted signs in Cambodia are those found on signboards. Examples on walls are almost non-existent. However, there is this large scale ghostsign discovered by Sebastien Ardouin of the Painted Signs and Mosaics blog. It looks very old but Sebastien dates it to the last ten years in this well researched blog post. He suggests that the humid tropical climate has led to this more extreme weathering
In a more modern take on the hand painted form on walls here is a sign that I saw last year, also in Phnom Penh. The site now features another sign for a competitor to this mobile phone brand.