Q.Our Live Oak Tree is in it’s 3rd year but this year it\’s leaves are very sparse. What do i need to do?
Our tree has been planted in the ground for at least 3 years. Prior years it seemed to grow extremely well, but this year it did not leaf out fully and seems to be unhealthy. The area where it is planted is well drained. What could be wrong with it and what should we do to promote it’s continued health?

I'm a California arborist so I don't know all the possibilities for your locale, but I do know that "oak wilt" disease is the big one for Texas.
https://texasoakwilt.org/
You may want to get a local arborist/PHC specialist (plant health care) to advise. There are treatment options available depending on stage if infection.
Another possibility is drought stress (water deficit) with the heat wave I've heard about in many parts of Texas.