If Austin is ok with you .... I would suggest the Goodwater Trail at Lake Georgetown.
Too hot at the moment, unless you just like sweating at night, but it's a 26.5 mile loop around the lake. It was built by the Army corps of engineers in the early 80's.
I probably won't go out there again until late October, but I'd be happy to meet you there and show you some of the better spots ....
There's also a 5 mile stretch at Round Rock, some great backcountry sites at the Hill Country SRA near Banderia Texas .... then there's Lost Maples, Enchanted rock, and several others ....
North of Houston there's the Lone Star Trail in the Sam Houston national forest ... a 100 mile long thru hike trail with a lot of great loops throughout the lobb lolly pines.
There's also the 20 mile long 4C trail in the Davy Crockett National Forest .... there's even a AT style shelter along that trail.
In West Texas you have the Mountains and some great remote hiking on up into Southern New Mexico and the Peco's wilderness and the San Monte de Christo range.
North in OK and ARK there's the Ouchita trail, which spans over two hundred miles and two states in the Ouchita Mountains.
Further North is several other trails in OK, including the Osark Mountain trail.