"I try my best," his dad says. "But he tells me, 'If I die on a racehorse, Dad, you'll know I died happy.' "
The kid goes on to spend as much time in the hospital with broken ribs, pelvis and whatever as he does in the winner's circle, and he wins a ton of races.
He breaks a foot early this year but is up in the morning and standing along the Los Alamitos Race Course rail on crutches, then on a cane watching riders and horses exercise.
He's back for maybe a month now, and it's five days before Christmas. He considers going to El Paso for the weekend to ride at the Sunland Park Racetrack, but there's a horse here he just loves at Los Alamitos.
And so he stays, his girlfriend of 11 years, Kristen Watanabe, who has her home decorated with pictures of her favorite jockey, on a pony now leading him and Harems Dynasty to the starting gate.
It will be the first race Harems Dynasty runs in her career, and less than 17 seconds from start to finish, her last.
On the schedule, it's only one of 11 races on a Saturday night Los Alamitos racing card, nothing unusual at the start, 300 yards as fast as four legs will carry a jockey to the finish line. And Sam Thompson Jr. is excited.
He's ridden Harems Dynasty many times in the mornings, telling Kristen at one point, "We're going to make headlines with this one." He has no idea.
The horse's trainer, Cody Joiner, saddles the well-bred promise, meets the jockey in the walking ring and tells him, "Good luck."
Expectations are running high. "He just loves that horse," who, Kristen tells her boyfriend jockey as they near the starting gate, "looks like she's warming up like a champ."
"Yeah, she is," Sam tells her, Kristen riding off to the barn to catch the race on TV.
But Harems Dynasty just isn't herself breaking from the gate, maybe a misstep and then a push to catch up, but as Joiner says, "75 yards into the race you can see Sam notices something is wrong."
Kristen notices too. "He never let the filly run. He's trying to take care of her."
Harems Dynasty finishes seventh of eight horses, Sam earning between $33 to $35 for the last ride of his life, the horse breaking a knee nearly 200 yards beyond the finish line, falling and rolling over the jockey.
A short time later the horse is euthanized.
Across the track, there's the sound of a siren. "I hear it," Kristen says, "but heavens no, I know it's not Sam. I saw the race."
But the horse never returns to the barn, Kristen beginning to worry, word arriving instead that the siren is for Sam.
Kristen gets to the parking lot just as the medics are bringing her boyfriend back to life.
IT IS Christmas morning, a time for giving, maybe the best Christmas some folks will ever know.
A team of doctors is ready. The decision has been made, Sam's father the last to come around, but now in complete agreement. The respirator will be turned off so some of Sam's organs might save others.
It's been five days since Sam's last ride, with him never regaining consciousness and two or three times requiring resuscitation.
Kristen is there every minute. "Putting together two chairs, as I've done so many times before for a bed," she says, the hospital a very familiar place for the girlfriend of a jockey.
The hospital hallway is caked in dirt, jockeys, grooms, trainers and owners arriving from the track and waiting and waiting for word, someone from their family now in a very bad way.
"He looks so beautiful when I first see him, like a prince who will wake up any time," says Donna McArthur, who almost always has Sam riding her horses.
He has so many friends, Mary Parsons says. "No, he's not a famous athlete making millions. And even though he wasn't a name most people might recognize, not even a 7-foot basketball player could walk as tall as Sammy."
He's only 36 years old, and he's "my best friend," Kristen says. "He just makes me laugh. Still. I sit here thinking of things, and I laugh.
"He's my rock," Kristen says, and then while recalling Sam's words, she adds, "we're a team."
She takes the next few days while everyone gathers from around the country to promise her partner she will do right by him and say goodbye, later adding, "I was lucky to have that."
But there is no hope save those who are counting on just that, maybe a pancreas or a new kidney.
"Sam's got such a good heart, he would want to save someone else," she says, and so papers are signed and it's Christmas morning, only three hours into a new day and somewhere the phone is ringing with of all things -- the best news.
Back in the hospital, "the respirator is turned off," Kristen says, "and his little heart just won't stop beating. He's in such good shape. It goes down a little bit, but then right back up."
His mother, his friend McArthur and Kristen sit with him, "and it's peaceful," Kristen says, no one saying anything. "It's so serene."
In time it's over, the doctors moving in quickly to make this Christmas one that won't ever be forgotten.
"I'm very proud of my son for the way he lived his life," his father says, "and very proud of him for being an organ donor. He was new life for someone else."