What would happen if she was outside of the fence with other dogs around? will they fight?

Yesterday it happened again but human this time. Two people came by and tried to play with the beagle. The lab snapped and bit the beagle's ear but afterward i checked the ear and didn't see any injury. I then saw a fresh mark on my lab's lip. I'm sure it wasn't there before this happened.

I'm trying some basic obedience training but don't have time to do it everyday. I also try to get the lab to socialize with people. She'd bark at them first and if they are calm she'd stop and turn away but if they scream or ran she would not stop barking until i pull her away.

btw. I live in rural Thailand. tried but still no luck on finding a professional trainer.