YES

We show the termination of the TRS R:

  f(x,f(a(),a())) -> f(f(x,a()),x)

-- SCC decomposition.

Consider the dependency pair problem (P, R), where P consists of

p1: f#(x,f(a(),a())) -> f#(f(x,a()),x)
p2: f#(x,f(a(),a())) -> f#(x,a())

and R consists of:

r1: f(x,f(a(),a())) -> f(f(x,a()),x)

The estimated dependency graph contains the following SCCs:

  {p1}


-- Reduction pair.

Consider the dependency pair problem (P, R), where P consists of

p1: f#(x,f(a(),a())) -> f#(f(x,a()),x)

and R consists of:

r1: f(x,f(a(),a())) -> f(f(x,a()),x)

The set of usable rules consists of

  (no rules)

Take the reduction pair:

  weighted path order
  
    base order:
  
      matrix interpretations:
      
        carrier: N^2
        order: lexicographic order
        interpretations:
          f#_A(x1,x2) = ((1,0),(1,1)) x1 + x2 + (1,3)
          f_A(x1,x2) = ((0,0),(1,0)) x1 + ((0,0),(1,0)) x2 + (1,1)
          a_A() = (3,1)
  
    precedence:
    
      f# = f = a
    
    partial status:
  
      pi(f#) = []
      pi(f) = []
      pi(a) = []

The next rules are strictly ordered:

  p1

We remove them from the problem.  Then no dependency pair remains.