BY LUAINE LEE

Knight Ridder News Service

Some might call it a demotion -- going from commander to movie director. But to Jonathan Frakes, it's a walk on the moon.

Frakes is best known as Cmdr. William T. Riker in TV's Star Trek: the Next Generation and four of the movies. But he transferred to the director's chair while he was still in his space-age tights. Directing the new film, Thunderbirds (which opens in South Florida Friday) is a melding of two elements of his acting experience -- technology and art. And Frakes seems born to the task.

To be a good director you need patience, a plan and a love of people, says Frakes. Those are qualities necessary in life, and the amiable Frakes seems to have them in spades.

''I was a psych major at Penn State and I signed up to be an usher at the summer theater,'' he says, in a 15th-floor hotel suite in Beverly Hills, Calif. 'And somebody in the theater department said, `You're a big guy, you want to be in this production of Arthur Kopit's Indians?' I said, `Yeahhhh.'

'I was 17 and saw how happy the professional actors were. It kept sinking in and I thought, `You think I could do this for a living the way they are?' So I went and changed majors and got that most useful of all possible degrees: a BFA in theater arts, which you know you can take to the bank,'' he laughs.

He spent a few meager years in New York sharing digs with his brother and splurging on frankfurters and beans. ''We'd chop up a wedge of cheddar, put it in the baked beans and chop up the hot dogs and put them in, and let it sit. That'd be good for two or three days,'' he says.

''I used to move furniture for a living in New York. My back is still screwed up from it. I was the worst waiter in the history of restaurants in New York. And I was Capt. Marvel. I used to go out in the street and open 7-Elevens. I never told anyone that. It's NOT on my resumé,'' he chuckles.

He played a troubled Vietnam veteran child beater on The Doctors and wangled a role in ''Shenandoah.'' At one period in '76 I was doing a soap by day at Rockefeller Center, and a Broadway show at night and thought I'd died and gone to heaven. I haven't had to take a straight job since. I was one of the lucky ones.''

The tall, bearded Frakes spent seven years in L.A. playing everything from the villain-of-the-week to browbeaten husbands when the audition for Star Trek: the Next Generation came along. ``We did 182 episodes and could've gone on for a few more years. Did four movies. And I still see the people. I [recently had dinner with Patrick [Stewart]. People are very loyal.''

Frakes, 51, is married to actress Genie Frances, and they have two children, a boy, 10, and a daughter, 7.

They met when they costarred in the miniseries, Bare Essence. ''But she was way too young for me then,'' he rolls his eyes.

''Then we did North and South and I was a bit of cradle-robber. I'm 10 years older than she. But we fell in love. We were on location in Charleston and Natchez, Miss. And we've been together for 19 years -- me and Genie,'' he sighs.

It was Frances (known to fans as Laura from General Hospital) who first encouraged him to push for directing opportunities on Star Trek. 'When I was waiting for [executive producer] Rick Berman to give me a slot, she's the one that said, `You keep going into the editing room because if you lose interest he's not going to give you a slot. If you want to do this you keep going. Go, go, GO.' She was great.''

Three years ago the family moved to London where Thunderbirds was made. Again, he says, it was because of Frances' generosity. 'I said, `I've had some offers but can't go because it's out of the country.' She said, 'That's it. I'm done (with General Hospital).' You want to hear what a good woman she is? I was in London working on the script for Thunderbirds and the producer said, 'We want to send you and the production designer to South Africa to scout locations.' I said, 'Great, OK.' I get to South Africa, they called and said, 'While you're out you might as well go to Australia.' So I had to sheepishly call Genie and say, 'I'm sorry, I'm going from South Africa to Australia.' So she had to pack up the kids, pack up the house, rent the house and move to London. And I was out with my two buddies flying around the world scouting locations. So I owe her big time!'' he laughs.