Absolutely not.
First, chickens are prone to sudden episodes of committing suicide. Chicks pop out of the shell, hard wired to look for new and novel ways of committing suicide. "Hey, Rudy... Watch this!" He says as he flies up and gets his head stuck through the fencing. A chicken can drown in a water bucket.
Second, the pond just might be a good home for intermediate hosts for a lot of internal parasites.
Third, mosquitoes.
Fourth, chicken poop. chickens poop everywhere. If your birds don't drown in the pool, they will surely be filling it with poop.