Is thick green clay like poop normal for my 7 month old?

Green Bowel Movement. Green bowel movements are usually due to rapid transit times and bile therefore being present in the stool. At this age it is most likely due to something the bay ate. I'm assuming you have started various solids. Red flags are bloody stools, black stools or lots of mucous.
Yes. As long as the stool contains no blood and has color it is fine. All the best. It likely reflects his diet.
Yes. Infant stools can be any color from the greens through yellows to brown. Consistency varies with the food ingested.