Thompson is 16 and has never played a down of organized football.
Yet, he's caused a bit of a stir on the summer high school football camp circuit, showing some uncanny quickness and athleticism for a player his size.
Thompson, who came to this country from Western Samoa last year, is 6-foot-7, 290 pounds. He's also an engaging young man to talk to, and has the sort of bloodlines that always catch the attention of college football recruiters.
It's that sort of profile that will no doubt catapult Thompson to major college recruiters' radar and will make him an intriguing prospect from the state of Washington's Class of 2013.
One of his cousins, Everette Thompson, is a starting senior defensive end for the University of Washington. Another cousin, Jason Thompson of Kennedy Catholic High School near Seattle, recently gave the Huskies a verbal commitment to play football there.
Thompson is surrounded by a wealth of football experience and knowledge. The Huskies have already started a dialogue.
"It's interesting how much my cousins love football," Desmoun Thompson said. "The love for football from them kind of rubs off on me. I just found a certain joy for the game. It's just fun."
Thompson will be a junior this fall at Kennedy Catholic, where his cousin Jason is the starting quarterback. Thompson will likely play on both lines for the Lancers.
He recently got some reps on the defensive line at the Five-Star Performance Camp at Auburn Mountainview High School and was happy with his progress. He said he's been to about 10 camps over the past year, including ones on the campuses of Washington, Oregon and Oregon State.
"I think this is the second camp I did at D-line," Thompson said. "So I'm catching on a bit. I feel like I learned a lot today."
Since he's never played football, he's also learned a lot from watching his cousins. But not in the way you might think.
Thompson has watched Jason battle his older brother Everette in NCAA '06 Football on PlayStation 2 on countless occasions.
Thompson said he has picked up a lot about American football from watching that video game.
"When they play NCAA, I just sit back on the couch and just watch them," Desmoun Thompson said. "And that helps me learn where their covers are. I learned that everything happens behind the line.
"I don't play hardly. When no one's watching, I might slip in a little game."
Jason Thompson expects big things from his cousin, who lives with him at their family's home in Renton.
"He'll surprise a lot of people because he's got a hard work ethic," Jason Thompson said.
Desmoun Thompson didn't play many sports in Western Samoa; just a little squash and rugby, and just for fun. He's excited about football. He plays a lot of catch with his cousin. At some point, he could see himself at tight end but is happy to learn the game in the trenches first.
"I never played football in my life," Thompson said. "When I first came over here, I was getting introduced to it. It started off slow then I found it fun just because I could play it. It was a sport that made me feel good and confident about myself and everything I did. I just enjoy it."