Gai Tom Kha or Tom Kha Gai as I remember the dish from my days at home in Thailand, is one of the classics. Because the soup is so simple to make, my mother made Gai Tom Kha when she ran out of ideas about what to have. My mother would send me to fetch some Galangal (Kha) from the bush around the side of the house. It's a root and I would have to dig down 6 inches to get it. It also has beautiful flowers that look like orchids. I've never grown them here in the US, but I bet you could from the roots you get fresh in the market, if you live where it's warm.
I can't grow them where I live, so my virtual Kha bush is a bag in the freezer, and now I also cook this soup when I'm out of ideas.
This is meant to have a milder flavor than a soup like Tom Yum Goong.