It sort of depends. Two facts are important here:
Firstly, SSDs only have a limited number of writes. They can be read any number of times without degradation, so the goal is to reduce writing as much as possible. We published an article that outlines the most common ways of reducing writes to the physical disk:
How to improve your computer performance and SSD life span with a RAM disk.
Secondly, RAM disks are volatile by their very nature, i.e. their contents disappear when you turn off or restart your computer. So if you place a portable app on a RAM disk, it will be gone after a restart.
There is a way to have persistent files on your RAM disk, but that means some writing to the SSD will still be necessary. Otherwise, the portable app files will need to be copied to the RAM disk after restart/power-on. For more information, please have a look at
RAM Disk user manual, particularly the
disk image files section.