Wipe the SSD of a barely-booting MacBook Air I have a Macbook Air (mid 2011) that had a RAM problem.

Sometimes it turns on, and while still booting macOS it would crash and hang forever due to bad RAM.

I want to sell the machine for parts, but I am worried about my data getting in bad hands.

I have a backup of every data stored in it but the disk isn't encrypted and it didn't had a login password.

I have it registered with iCloud but It seems that the remote wipe option wasn't set.

I NEED a way to do a wipe of the contents stored on the SSD, is there a way I can do that without opening the machine?

There is a sequence of characters that will wipe the machine while booting? or maybe a Linux USB drive that does that? The machine is sometimes up for 5 seconds or so until it freezes and turns itself off.
You could try to hold down Command + R as soon as you start up your MacBook. This will get you into recovery mode. From there you can start the Disk Utility and format your disk.