  In a previous paper we have investigated the molecular environment towards
the eastern border of the SNR G18.8+0.3. Continuing with the study of the
surroundings of this SNR, in this work we focus on its southern border, which
in the radio continuum emission shows a very peculiar morphology with a
corrugated corner and a very flattened southern flank. We observed two regions
towards the south of SNR G18.8+0.3 using the Atacama Submillimeter Telescope
Experiment (ASTE) in the 12CO J=3-2. One of these regions was also surveyed in
13CO and C18O J=3-2. The angular and spectral resolution of these observations
were 22", and 0.11 km/s. We compared the CO emission to 20 cm radio continuum
maps obtain as part of the Multi-Array Galactic Plane Imaging Survey (MAGPIS)
and 870 um dust emission extracted from the APEX Telescope Large Area Survey of
the Galaxy. We discovered a molecular feature with a good morphological
correspondence with the SNR's southernmost corner. In particular, there are
indentations in the radio continuum map that are complemented by protrusions in
the molecular CO image, strongly suggesting that the SNR shock is interacting
with a molecular cloud. Towards this region we found that the 12CO peak is not
correlated with the observed 13CO peaks, which are likely related to a nearby
\hii~region. Regarding the most flattened border of SNR G18.8+0.3, where an
interaction of the SNR with dense material was previously suggested, our 12CO
J=3-2 map show no obvious indication that this is occurring.
