Aldon Smith didn't have any notable health issues before he died suddenly last week ... so says the barber who just cut his hair.

We spoke with Tee Maultsby -- Aldon's barber who interviewed him on an episode of his "Laced Up" podcast -- said he even joked with Aldon recently that the dude still looked like he could dominate on the defensive side of the ball.

Tee says Aldon never said anything about being sick to him -- on or off camera -- and he says Aldon was in the process of turning his life around in recent months.

Maultsby also tells us Aldon aimed to use his platform for mental health advocacy prior to his passing.

As you know ... Smith was reportedly found unresponsive in a truck shortly before he was pronounced dead on Saturday.

Smith had spent the day delivering pizzas to a local homeless outreach organization in the hours before he died. His friend, Amir Shirazi, delivered the pizzas with him ... and later found him slumped over in the front seat of the truck.

A cause of death has not yet been determined ... but Aldon's family has said they want to have his brain tested for CTE.