I personally like button mushrooms. Shiitake mushrooms also work well. But honestly, there are so many excellent mushrooms out there these days that you can choose your favorites. Oyster, lion's mane and creminis are all tasty in their own right. Both fresh and dried mushrooms can be added. For dried mushrooms, rinse them thoroughly and soak them in warm water for a couple of hours. The brodo (mushroom soaking liquid) is a potent flavor booster, so feel free to add some to your Thai coconut soup or save it to make risotto later. I also add shiitake mushroom powder for even more umami, but you can omit it if you do not have it.