I found a way after googleing a bit smarter (it was difficult to find the correct search keys).
In short, the file
/proc/acpi/wakeup has a line for
LID which is enabled.
$ cat /proc/acpi/wakeup
Device S-state Status Sysfs node
PCIB S4 disabled pci:0000:00:1e.0
USB1 S3 disabled pci:0000:00:1d.0
USB2 S3 disabled pci:0000:00:1d.1
USB3 S3 disabled pci:0000:00:1d.2
USB4 S3 disabled pci:0000:00:1d.3
USB7 S3 disabled pci:0000:00:1d.7
MODM S3 disabled
HDEF S3 disabled pci:0000:00:1b.0
PXS1 S4 disabled pci:0000:02:00.0
LID S4 *enabled
echo " LID" > /proc/acpi/wakeup it will change to disable and the computer won't wake up on lid open.
Follow the instructions on the already mentioned link to set it permanent on your computer.