This is nice: it's a get I'd want to take for a rogue, and with one feat it gives a whole different build/playstyle -- nice. Awesome for a rogue half-orc, and with a 1-level dip in fighter.
1. I'd say the STR bonus isn't needed, though I'm going to suggest two limits below, so in the end it might be needed. But I still think no.
2. Really good. I'd suggest limiting it to a one-handed weapon (to avoid GWF cheese); possibly one-handed or "versatile".
3. Fun. I'd specify that the intimidation attack takes the bonus action. I think the standard wording is something like "...until the end of your next turn."
Part of my reason for wanting to allow great weapons is selfish, as I had a Spring Attacking Fighter/Rogue in 3rd Ed who used a holy great sword.

The intimidation check is supposed to use the bonus action, though I could make it a little clearer in the text. Okay, re-worked a bit:
Thug
- You gain +1 to Strength, to a maximum of 20.
- You may perform a sneak attack with any one-handed or versatile weapon in which you are proficient, provided you meet the other requirements.
- Whenever you hit an opponent with a sneak attack or critical hit that deals damage, you can use your Bonus Action to make a Charisma (Intimidation) check against that opponent. If successful, the opponent has disadvantage on attack rolls against you until the end of your next turn.
I like keeping the Strength bonus in there to make it still somewhat attractive for non-rogues. I could see some fighter or barbarian types who don't care about sneak attack possibly picking it up for the intimidation effect.
My other thought would be to drop the Strength bonus, but allow the Intimidation check to use the player's choice of either Charisma or Strength.