LeBron James -- TRAPPED IN HAIR-LOSS DENIAL ... Says Kenny Smith

LeBron James is losing a battle with nature ... and he needs to stop fighting ... so says Kenny Smith, who tells TMZ Sports LBJ should lose the headbands and ACCEPT HIS BALDNESS ALREADY!!!

Smith is a hair loss expert (look at him) ... in fact, Kenny and the gang at "Inside the NBA" were the first to notice that LeBron was using his headband to hide his rapidly receding hairline.

Now, Smith tells TMZ Sports ... the jig is up -- 'Bron should just pull a Mr. Clean and just shave the rest of it off already before he starts to look like Larry David.

"I'm from the school of thought [where] I let things go before they let me go."

Truth hurts, LeBron.