Tristan Thompson is opening up for the first time about his mother's unexpected death ... penning her an emotional tribute letter on Instagram, writing his "soul is empty" since her passing.
"Dearest mommy in heaven, It has been one month since you’ve been gone," the former NBA player wrote.
"I’m in disbelief. I'm in the deepest part of sorrow & grief. My soul is empty as I come to terms that my biggest supporter/superhero is gone."
The 31-year-old continued, writing about the sacrifices his mom made for him and his siblings.