Gastelum revealed his plans Tuesday.
"I'm excited," Gastelum said on Facebook. "Another challenge is always good."
The fight will be Gastelum's first since April 13 when he upset highly touted Uriah Hall by split decision in a TUF 17 finale. Gastelum has a pro record of 6-0.
Thiago (15-5) has lost four of his past six fights. He snapped a two-loss streak on May 18 with a unanimous decision over Michel Richard dos Prazeres.