My 12 yr old son is currently using "Yousician" to teach himself guitar.  It generally works quite well, he studied piano for one year so he can read music already.  Yousician does have some limitations in terms of accuracy but it is fine for now.  I think in a few more months it will not be suitable. 

 

I'm wondering if there are other and better online guitar sites out there?

Several months ago I looked for the same for a 14 Y.O boy.  I couldn't find any Thai language guitar instructional videos that had decent presentation, organization or continuity. There are a few 2 or 3 video series but they were hard to follow and not well thought out.

There are a few series on DVD available at many guitar shops but there seemed no way to check them out without buying them.

The kid I was doing it for got lucky and found a teacher at his school who was willing to teach him for a reasonable B100/hr.   If there are any guitar shops in your area, they might be able to suggest a teacher.