Khao Daeng (in Thai "เขาแดง") is the viewpoint of Khao Sam Roi Yot National Park area and 1 of 10 things must be visited.
About 300 metres trail to the top, just follow the yellow arrows. At there you can get a breathtaking view of the surrounding coastline (and a fair number of rice or shrimp farms). My last visit in the afternoon, the whether was really hot as shown in pictures. So I recommend to visit at dawn to catch a glimpse of the sunrise from the sea, and watch the wildlife come out for breakfast. There are monkeys on the way to the top. No feeding the animals though!
Important: please bring the waste bottled water down to save the environment ^^