American actor David Hasselhoff is a busy man.

The 62-year-old has just wrapped up a self-produced comedy called Killing Hasselhoff, filmed a short appearance in upcoming comedy film sequel Ted 2 and launched an iPhone game called Hoff Zombie beach.

On Thursday, his latest television documentary, Hasselhoff Vs The Berlin Wall, will premiere on the National Geographic Channel.

The star, best known for playing lifeguard Mitch Buchannon in the 1990s TV series Baywatch, and high-tech modern crime fighter Michael Knight in 1980s TV series Knight Rider, unabashedly admits that he is "just a guy who's happy that the phone is ringing", even if some of the projects he is involved in make comical references to his past roles.

Speaking to journalists in a teleconference call from London, where he is now shooting Hoff The Record, a comedy based on his life, he says: "I'm kind of just enjoying the world because people know who I am. If they didn't know who I was, the phone wouldn't ring.

"It's not about the money. Money doesn't buy you happiness. Happiness is the journey. I'm still on an incredible journey."

His showbiz career started in the early 1970s with a role on the American soap opera The Young And The Restless. But he shot to international stardom with his role in Knightrider and then Baywatch and its spin-offs Baywatch Hawaii and Baywatch Nights, which ran throughout the 1990s.

Hasselhoff, who also sings and has released a slew of solo albums over the past two decades, continues to pursue music in Celebrate The 80s And 90s With The Hoff, a touring show which features artists from that era, including Rick Astley, the Vengaboys, Samantha Fox and 2 Unlimited.

On his recent documentary film project, he takes viewers on a personal journey to Berlin. Retracing the wall's history, he speaks to people who share stories on the divide between East and West Germany, the subsequent fall of the Berlin Wall and its impact on the country.

He has a connection with the wall, having famously performed his hit song Looking For Freedom before hundreds of pro-German reunification activists at the wall on New Year's Eve in 1989, a few weeks after it started being taken down.

He recalls: "I asked the people in East Berlin: 'How do you know me? You know me as the man who talks to the car (in Knight Rider)?

"They said: 'No, we know you as the man who sings about freedom'. That really moved me."

He says the documentary will retrace the stories of the first person who was killed and the people who escaped from East to West Germany, as well as "the death strips and how the wall began".

The actor, who is divorced with two children, says: "I know they are heroes. I play heroes. Maybe I'm a hero once in a while because I can help someone or change someone's life as I can take a picture or give him an autograph.

"But these are the real heroes who risk their lives for their families to escape."

Hasselhoff Vs The Berlin Wall premieres on Thursday at 10pm on the National Geographic Channel (SingTel mio TV Channel 201, StarHub TV Channel 411).