Greg Olsen's Son Speaks from Hospital After Heart Transplant, 'Thanks for Praying for Me'

Greg Olsen's 8-year-old son is speaking out after his heart transplant ... and the kid is simply incredible.

"Hi everybody, thank you for thinking of me," TJ Olsen said in a video shot from his hospital bed and posted Monday morning.

"Thank you for praying with me. Congrats, all of you have gotten a win! We love you guys!"

TJ underwent his heart transplant surgery on Friday -- and his ex-NFL star father said doctors at Levine Children's Hospital in Charlotte, NC were "very happy" with the way things went.

Greg also noted TJ would "be sedated for a few days but his road to recovery has begun."

Now, TJ is up and talking -- AND CHARISMATIC AS EVER!

Think about what he's been through over the past few days/weeks -- and to be able to sit up in your hospital bed and talk make a video thanking a bunch of strangers?

This kid is incredible.

TJ was born with a serious heart condition -- and underwent 3 open-heart surgeries before his 3rd birthday.

Just a few weeks ago, Greg announced TJ's heart was "reaching its end" -- and he needed a heart transplant ASAP.

After the procedure, Greg issued a statement sending love to the donor family for their gift of life.