Pine Tree Forest
North of Samila beach, the peninsula where Songkhla sits narrows down to a thin cape of land. Much of this area is given over to a small forest of Casuarina pine trees. On some maps, it's labeled a garden, but aside from the brick path running through it the area is mostly untended. If you're adventurous, you can get off the path and make your way down to the beach, where you'll have a long stretch of sand all to yourself, even on a weekend.
The forest runs from Samila beach all the way up to the Aquarium. At the very southern end is a large playground for children. There's a large structure shaped like a sailing ship, with slides, ropes and other things to keep kids occupied. I had trouble resisting having a go at it myself.