FIG. 1 is a perspective view of a boom extension arm in accordance with the present invention;

FIG. 2 is a right side elevational view of the boom extension arm of FIG. 1, the left side elevational view being a mirror image of the right side;

FIG. 3 is a front elevational view of the boom extension arm of FIG. 1;

FIG. 4 is a rear elevational view of the boom extension arm of FIG. 1;

FIG. 5 is a top plan view of the boom extension arm of FIG. 1; and,

FIG. 6 is a bottom plan view of the boom extension arm of FIG. 1.

The broken line showing of portions of the design and of environment forms no part of the claimed design.