It is said that Southeast Texas is overrun by wild boars. However, I have only seen sign of them within national park borders-where hunting is not allowed-and all google search results return paid hunting ranches which I regard as "pig farms". Where can I go hunt wild pigs in southeast Texas without paying?
Short answer: there's a lot of public land, most likely state owned (not federal), that's available for hunting.
There might be limitations for nonresidents and/or based on what you plan to hunt with (e.g. firearm, black powder, bow) but this looks like a great starting point for information:
Public Hunting and Access to TPWD Lands
"Texas Parks and Wildlife Department (TPWD) offers a variety of hunting opportunities through two public hunting systems."
Here's the Texas page for licensing: http://www.tpwd.state.tx.us/business/licenses/online_sales/
Here's a breakout of licenses with associated fees for both residents and non-residents: http://www.tpwd.state.tx.us/business/licenses/public/recreational/index.phtml
If you can add a bit more information about what you're looking for I can try to be a bit more specific.
Side note, as for search terms try, "texas game and wildlife hunting license" and "texas public hunting land". I suspect you'll get fewer ranch ads if you're specifically including the word "public" in your query.