In this study we present the results of a Regional Coupled ocean-atmosphere Model (RCM) simulation of the South Asian Summer Monsoon (SASM) forced by global atmospheric and oceanic reanalysis at 20 km grid spacing over a period of 25 years (1986-2010). The RCM shows a more realistic alignment of the simulated rainfall along the orographic features of the domain. Furthermore, the RCM simulates the observed feature of convection over continental SASM region being more vigorous with dominance of mixed warm and cold phase hydrometeors in contrast to the dominance of the warm rain process in the neighboring tropical oceans. Similarly, the upper ocean features of contrasting mixed layer and thermocline depths between the northern and equatorial Indian Ocean are also simulated in the RSM-ROMS. Intra-Seasonal Oscillation (ISO) of the SASM at 10-20 and 20-70 days are simulated in the RSM-ROMS with many of the observed features captured like the latter frequency band being of higher amplitude and the meridional propagation being slower in Bay of Bengal compared to that over Arabian Sea. Additionally, RSM-ROMS shows 12.3 Monsoon Low Pressure Systems (LPS) per season that is comparable to 14.6 per season from observations. Furthermore, the intraseasonal contrasts of LPS between the wet and dry spells of ISO is also reproduced in the RSM-ROMS. The simulation of mesoscale LPS and its intraseasonal variability by the RCM amidst its reasonable fidelity of the SASM climatology clearly demonstrates the value addition of downscaling a global reanalysis at 2.5° (~277-km) to 20-km grid spacing.