YES

---- CR(R)
---- [Knuth and Bendix, 1970]
R:
a(s(x)) -> s(a(x))
b(a(b(s(x)))) -> a(b(s(a(x))))
b(a(b(b(x)))) -> a(b(a(b(x))))
a(b(a(a(x)))) -> b(a(b(a(x))))
CP(R):
a(b(a(s(a(___y7))))) -> b(a(b(a(s(___y7)))))
b(a(b(a(b(s(a(___y13))))))) -> a(b(a(b(a(b(s(___y13)))))))
b(a(b(a(b(a(b(___y21))))))) -> a(b(a(b(a(b(b(___y21)))))))
a(b(a(b(a(b(a(___y31))))))) -> b(a(b(a(b(a(a(___y31)))))))