We report an improved measurement of D+→KS0K+ and Ds+→KS0π+ branching ratios using 605 fb−1 of data collected with the Belle
detector at the KEKB asymmetric-energy e+e− collider. The measured
branching ratios with respect to the Cabibbo-favored modes are B(D+→KS0K+)/B(D+→KS0π+) = 0.1899±0.0011±0.0022
and B(Ds+→KS0π+)/B(Ds+→KS0K+) =
0.0803±0.0024±0.0019 where the first uncertainties are statistical and
the second are systematic