For those who need SCIM while running 32-bit apps on a 64-bit system outside chroot, there are two things (at least for me) needed.

Apart from the obvious that you need SCIM installed in the 32-bit chroot, you’ll need to set SCIM_MODULE_PATH to point to the 32-bit SCIM libdir. For instance, my iceweasel32 script looks like:

#!/bin/sh
export CHROOT=/chroot/testing.32

export GTK_PATH=${CHROOT}/usr/lib/gtk-2.0

export LD_LIBRARY_PATH=${CHROOT}/lib:${CHROOT}/usr/lib:/lib32:/usr/lib32

export SCIM_MODULE_PATH=${CHROOT}/usr/lib/scim-1.0

export MOZ_PLUGIN_PATH=${CHROOT}/usr/lib/mozilla/plugins

linux32 ${CHROOT}/usr/lib/iceweasel/firefox-bin "$@"

Secondly, you’ll need to add a symlink in /usr/lib32/gtk-2.0/2.10.0/immodules for the chroot’s /usr/lib/gtk-2.0/2.10.0/immodules/im-scim.so. Not the cleanest way I have to say, but it works.