Hi there Stephen. Long-story short: there is no pre-made solution for this in any version of RHEL. (You didn't mention what version of RHEL you're on, but I'm assuming 6...?)

If I needed to do this, the way I would approach it is with a custom script that uses grubby, e.g.:

[root@r67 ~]# ls -l /usr/local/sbin/Sreboot
-rwx------. 1 root root 1394 Oct 23 10:11 /usr/local/sbin/Sreboot

[root@r67 ~]# cat /usr/local/sbin/Sreboot
#!/bin/bash
# Sreboot v0.0.0 last mod 2015/10/23
# Ryan Sawhill Aroha <rsaw@redhat.com>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
#    General Public License <gnu.org/licenses/gpl.html> for more details.
#-------------------------------------------------------------------------------

if ! grubby --update-kernel=DEFAULT --args=S; then
  echo Error using grubby to modify default kernel to boot to single-user mode
  echo Aborting ...
  exit 2
fi
echo Modified default kernel to boot to single-user mode
echo Relevant kernel line:
grep --color -w S /etc/grub.conf
echo

cat >/etc/cron.d/grub-disable-single <<EOF
@reboot root /usr/local/sbin/grub-disable-single
EOF

cat >/usr/local/sbin/grub-disable-single <<EOF
#!/bin/bash
/sbin/grubby --update-kernel=ALL --remove-args=S
/bin/rm /etc/cron.d/grub-disable-single 2>/dev/null
EOF
chmod 700 /usr/local/sbin/grub-disable-single

echo Configured crond to disable single-user mode after next multi-user boot
shutdown -r +1

Here's what it looks like:

[root@r67 ~]# Sreboot 
Modified default kernel to boot to single-user mode
Relevant kernel line:
    kernel /vmlinuz-2.6.32-573.el6.x86_64 ro root=UUID=cf39816d-004e-4422-b32d-001afb92ba1a rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD console=ttyS0,115200 console=tty0 console=ttyS0,115200 rd_NO_PLYMOUTH crashkernel=auto SYSFONT=latarcyrheb-sun16  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM S

Configured crond to disable single-user mode after next multi-user boot

Broadcast message from root@r67.example.com
    (/dev/ttyS0) at 10:12 ...

The system is going down for reboot in 1 minute!

...

Setting hostname r67.example.com:  [  OK  ]
Setting up Logical Volume Management: [  OK  ]
Checking filesystems
Checking all file systems.
[/sbin/fsck.ext4 (1) -- /] fsck.ext4 -a /dev/vda3 
/dev/vda3: clean, 39108/294912 files, 374665/1179392 blocks
[/sbin/fsck.ext4 (1) -- /boot] fsck.ext4 -a /dev/vda1 
/dev/vda1: clean, 38/32768 files, 14885/131072 blocks
[  OK  ]
Remounting root filesystem in read-write mode:  [  OK  ]
Mounting local filesystems:  EXT4-fs (vda1): mounted filesystem with ordered data mode. Opts: 
[  OK  ]
Enabling local filesystem quotas:  [  OK  ]
Enabling /etc/fstab swaps:  Adding 1048572k swap on /dev/vda2.  Priority:-1 extents:1 across:1048572k 
[  OK  ]
init: rcS main process (350) terminated with status 1
[root@r67 /]# runlevel
N S
[root@r67 /]# init 3

...

Red Hat Enterprise Linux Server release 6.7 (Santiago)
Kernel 2.6.32-573.el6.x86_64 on an x86_64

r67.example.com login: root
Password: 
[root@r67 ~]# tail -1 /var/log/cron 
Oct 23 10:16:09 r67 CROND[1589]: (root) CMD (/usr/local/sbin/grub-disable-single)
[root@r67 ~]# date
Fri Oct 23 10:16:39 EDT 2015
[root@r67 ~]# cat /etc/cron.d/grub-disable-single
cat: /etc/cron.d/grub-disable-single: No such file or directory
[root@r67 ~]# grep -w S /etc/grub.conf 
[root@r67 ~]#