The easiest and safest way would be to just press TAB in refind after you select what to boot (this screen). This opens a sub-menu where you can tell refind to boot the LTS kernel.
The more advanced but - in the long run - also more comfortable way would to configure Scratch that, do what YoYo says and don’t forget to backup the file first! /boot/EFI/refind/refind.confaccordingly. To find your PARTUUID, use lsblk -f
I believe there is also another way, but that method fails as soon as some or all of your kernels are upgraded next time. Also, it’s dangerous when done wrong so I’d rather not talk about it 
PS: of course you could also uninstall the Cachy kernel with the Cachy Kernel Manager or pacman