As has been noted, you cannot safely render someone unconscious. Even disabling techniques such as tasers carry a risk of killing. There's a reason that most people refer to such weapons as "Less than Lethal" weapons, not 'Non-lethal.'
Frame Challenge: You don't need to knock them out
In fact, you shouldn't. You have super strength. Even for a normal-strength person, any physically-based means of rendering someone unconscious carries a risk of damage or death. You are strong enough to (potentially) tie steel girders into pretzels. The difference between 'hard enough to knock out' and 'hard enough to kill' is pretty minor by your standard.
So, you do what the police do.
You learn how to restrain, not knock out. You put someone into a position where their mobility is extremely limited, and then you lock them in that position. This is why the police carry handcuffs and zip ties. All of these things are available for sale on the open market, go buy a bunch. Then practice, practice, practice. Handcuffs and double-loop zip tie cuffs are extremely fast to apply if you have used them enough. Heck, just look at how fast a cowboy at a rodeo can hogtie a steer.
The advantage you have with your super strength and durability is that you can easily hold a criminal nice and still so you can apply the restraints quickly and easily, and all of their flailing about isn't going to hurt you.
So...when you go into a situation full of 'random thugs' it should look less like your standard superhero going in punching and flailing. You should just move from criminal to criminal, breaking their weapons, setting them face-down on the ground, then positioning their arms and legs behind them and tying all four appendages together.
Someone who is that thoroughly restrained is not likely to be any more of a threat than someone who is unconscious. If their weapon is in pieces and they can't move...they are subdued. No need for the risky proposition of rending them unconscious.
(Note: This is sort of like how Spiderman handles crooks. He doesn't have to knock them out...he just hits them enough to daze/disarm them, then webs them to a solid object til the police arrive)
In short, it should look more like a hogtying competition at a rodeo than a proper fight.
Heck, as a Super, you could probably even get a company to 'endorse' you and manufacture 4-strand heavy-duty zip tie cuffs designed specifically for that purpose.