The play "Picnic on the Battlefield" also known as "Pique-nique en campagne" is indeed a representative of the theater of the absurd because it includes two of the staple themes of this genre which are:
The combination of tragedy and comedy (which is also found, for example, in Samuel Beckett's play "Waiting for Godot".)
The topic of life as a meaningless journey.
The inevitability of feelings of loss, purposelessness, and bewilderment.
The nonsense of reality; disjointed, meaningless.