Savedogs will get it for you, and thanks for helping the poor guy.
We use different methods, depending on the situation, but things will be much easier when we ship over humane traps from the States.
If you can get close enough, loop something over the dog’s head (we have a dog-catching pole). This works fine if you can get close enough.
If the dog avoids the ‘noose’, the next thing to do is to chase the dog down; many dogs will stop running and cower on their backs, ready to defend themselves, and this is the ideal chance pin the dog down by its neck using the stick while grabbing for the scruff. You can try to calm the dog at this point, as many will now let you handle them as they feel you have domintaed them (they are in a submissive position). Lots of dogs who tried to bite me just accepted their fate once they’d gone to their backs.
Another method is to put food in a wire cage; have wire tied to the door and fed through the roof of the cage so that you can pull the door shut from behind. A wire cage is better than a crate, as it doesn’t seem like a confined space to a dog.
If you can get your hands on some, you can buy a quick-working sedative from the States that you can put in the food; it will knock the dog out in about 20 minutes. Savedogs also use a tranquiliser gun or blowdart. Both of these methods should be used with caution, by someone with experience.
Other methods that animal welfare groups use in Asia are a net - literally a huge butterfly net, which you can throw over the dog. Once again, if the dog becomes really scared while not too far away, it might turn and cower ot bear its teeth, and this is an excellent time to use the net. Some groups prefere to use a sack, as it blocks the dog’s vision, which helps to calm it. We’ve used a duvet in a similar fashion and it worked well.
In some situations, you will have the dog pinned down or draped in a net or blanket, and just by talking calmly and reassuringly to the dog while asserting your dominance with your stance and position over the animal, you can start to get ut used to your touch, by tickling the base of its tail, then slowly moving up. Do this carefuly and watch the eyes and the lips for signs that the dog will try to bite. A sharp ‘Ah ah’ will actually stop many attempts. If you can start to stroke the scruff of the neck, you are in an excellent position to get a muzzle on the dog, which must be done slowly but deliberately. You’d be surprised how many dogs will let you do this once you’ve dominated and calmed them.
You can also lay a net on the ground and put food in the middle, and rig up some way to pull up at least two adjacent corners as the dog steps in.
Finally, you can often just walk up to the dog and put a collar and leash on it - by far the best method, if the dog is willing. 
This is actually quite easy to do if you gain the dog’s trust over time, and this method has proved very effective for us in the past. The best person to do this is the one who has been feeding it.
I’m sure there are more ways, but I can’t think of any right now. In all cases the key is to wholeheartedly commit to the act of capture; any animal will take huge advantage of your hesitation or uncertainty.
Good luck, and keep us posted. (And do be extremely careful about being bitten; it does happen.)
I almost specified in brackets but I figured it was obvious. 
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