Fix a seam under the pocket of my pants?

Since I don't know anyone whose willing to sew for no money at all (at least in the vicinity) I figured I'd have to learn some way of dealing with this (yearly) problem:

I'd like to use a needle and some tan thread to fix some pretty heavily used khaki pants. I have never sewn clothing or dealt with thread in any other way than to make loops out of metal for holding chicken coop fences together or to make loops for holding animals in a specific place. (Foolishly perhaps?) I expect to get a good decade of use out of the clothing I own.

I can see the holes where the thread's unraveling. It really sucks because that thread's going to be more and more unraveled as I use the pants more and the hole's going to be more and more of a problem.

Please don't leave any details out?

How do I fix a seam that's started to come out -- that's located directly under my khaki pants pocket? How tight should I make the thread? Is there any specific loop I can Google? How did the factory worker in Guatemala do it?