Thresh bug

I think that is true, ive seen a thresh that couldnt execute like 300 health minions with a 500 exucute. So i think it may be true

I can confirm as well. I've been using Thresh for the last 2 days and the passive on relic shield doesn't execute. It sometimes does after I use flay.

Thresh is not a melee. He is counted as ranged. This is why.

Dont think that is right. It has worked before this patch....you can see it working on live streams from Krepo before the patch.

His passive on his e makes it look like an execute if you charge it up. Thresh is ranged and does not execute

Not a bug. Thresh, being classified as a ranged champion (even if he uses his melee-range attack animation), does not get the benefit of the execute damage, which is specifically stated in the tooltip as being melee-only.

This does not stop Thresh from taking advantage of the rest of the Relic Shield effect, however; if he kills a minion, he will still expend a charge, gaining gold and health for both him and his nearby ally. The only difference is that he (and all other ranged champions) do not get any bonus damage to help them kill the minion.

Thresh is counted as a ranged champion (easiest way to confirm is that his autos are blocked by Braum's E and Yasuo Windwall). Relic Shield passive only works with melee champs.

The reason that it seemed Krepo was "executing" minions is that his auto was most likely empowered by the Flay passive (deals bonus magic damage based on souls collected + downtime in between autoattacks), which essentially killed the minion without the passive.