Does not despawn immediately upon daybreak.

Here is a video of him. Not me in the video:

https://www.youtube.com/watch?v=TBBXVzEjyS0

I found him once thoug, some months ago, but I gave up. My gear is way better now. I found him on the way between Pilgrims Haven towards Valencia city. Closer valencia city than pilgrim.

Here is some more info about his spawn locations and walking paths that Korea has gathered:
https://www.reddit.com/r/blackdesertonline/comments/5htde7/screenshots_of_every_laytenn_spawn_i_encountered/

https://imgur.com/wTVR3F6
https://imgur.com/t3iVDFp

These are 2 location i found them, they appear only after 10PM

So my friend and my was looking for an S letter on this one today, we got it in 11 layten total (I got S grade 4th time and my friend got it after the 6th tries). (approximatly +120% chance of knowledge and +25% chance of higher tier knowledge)
Here is how we did to hunt layten "easily":
You must go on the spot that i describe before its night so before 10:00 PM in game time. The layten spawn at 10:03 , it rise from the ground. If you go there early you'll find it without any problem 100% sure! But if you wait you may not find it as their is some sort of bots that farm those mobs!!! (i saw i myself without record, they teleport and walk under the map?!?!?! (and its not hystria or aakman!!!), they do one shot the layten)...

So you must use the abstinence sanctum aswell as sincerity sanctum in order to align you correctly. Then u'll get near a clear triangle like shapes you must go on the bottom left of this shapes. If you see 2 small scorps well done you are at the right spot! stay close the southest one and layten spawn right there! After spawning it will travel a bit in the area , beetwen the 2 scorps, but like the horse when he is too far from his spawn he will run back toward his spawn so don't worry he wont go far into the desert!
Once you have found the spot you can switch channel!!! You'll get an additional layten for each channel, so guild channel is a go to in this case! Doing that you'll easyly get 4 layten each night (starting on a non-guild channel then witching into guild channel).You may get more if you look for him to respawn but i never saw it spawn more than once in a single night from a specific channel.
Clearly dont forgot looney/weenie elixir, simple cron food , pets/artifact and pearl outfits because it help a lots.
Here is the pics that i took in order to help you locate this sweet spot:
https://imgur.com/a/3wR28zZ