Watch the 1 5 1 Structures online guitar lesson by Brad Carlton from Guitar Lab: Open String Universe
Our first chord is A root 5th root structure rooted off the open 5th string. The 2nd string open is a B which is the 9(2) in the key of A and the 1st string open is an E which is the 5 in the key of A. The total formula of this voicing is 1 2 5 therefore it is an Asus2. The formula 1 2 5 is a subset of the following scales: ionian, dorian, lydian, mixolydian, aeolian, melodic minor, overtone, mixolydian b6. 1 2 5 would also be a subset of major pentatonic so try all of these scales to hear your melodic possibilities. The included chart shows this chord/scale relationship for the sus2 harmony.