The Welsh legend, who was born on 7 June 1940, said he did not mind growing old because "the memories are tremendous".
And he said lockdown reminded him of his own two-year isolation with tuberculosis from the age of 12.
"I sympathise with young people that can't go and play," he said.
Sir Tom, who grew up in Pontypridd, enjoyed huge commercial success with hits including It's Not Unusual, What's New Pussycat? and Kiss.
He became one of the world's biggest stars, with his live Las Vegas performances earning the admiration of Elvis Presley and Frank Sinatra.
Throughout his career he has constantly reinvented himself, moving from pop, rock and country to gospel, soul and blues and then on to electronic and dance music.
Speaking to friend and fellow-singer Cerys Matthews for BBC Radio 2, he said: "The memories are tremendous and I don't want to stop.
"To reach 80 and to have such wonderful memories and to be still doing it and still making a point, or trying to - thank you to everybody that has been with me, the audience.
"You can't express yourself properly unless there's people there to listen to you.
"God has been good to me and my voice is still there. So as long as it's there I wanna get up... singing live to people is the thing."
The current lockdown means his birthday celebrations might be limited, but Sir Tom has experienced self-isolation before, having been kept at home in a single room for two years after his TB diagnosis as a child.
"With this lockdown now, I'm thinking 'my God, how are those kids coping?' because I remember it," he said.
"It taught me not to take health for granted."