A new and distinct cultivar of Begonia plant named ‘;KRSWESA01’; characterized by its compact, broadly upright and mounded plant habit; moderately vigorous growth habit; moderately freely branching habit; dark green to greyed green-colored leaves; freely flowering habit; semi-double to double-type male flowers and single-type female flowers that are light salmon red in color and held above and beyond the foliar plane; and good postproduction longevity.