His career in baseball started at age 6 when asked to participate in a tee-ball game, and he hit a home run in his first at-bat.

He was 7 for 26 with a homer as the primary Australian RF in the 1997 Intercontinental Cup when the country won its first Medal (a Bronze) in a worldwide event.

Kingman's career really took off in 1997–1998 when he broke every ABL record in the Triple Crown categories with a .487 average, 28 home runs and 66 RBI (tied for the lead).

Grant Balfour was credited with the save in the bottom of the 9th after closing down the formidable Cuba line-up, the final out recorded with a K2.

Kingman produced at a .429/.500/.476 clip in the 2005 Baseball World Cup, finishing fifth in the tournament in batting average.

Kingman was 1 for 5 with 2 strikeouts and an RBI for Australia in the 2006 World Baseball Classic, playing one game at third instead of Glenn Williams and pinch-hitting once for Dave Nilsson.

Kingman was back for the 2008 Final Olympic Qualification Tournament, going 6 for 15 with a walk, 2 doubles and 6 RBI while splitting first base duties with Williams.

Australia went 4–3 in the tournament and failed to earn a spot in the 2008 Olympics Kingman's battle with injuries has forced him into a temporary premature involuntary retirement from representative baseball following the 2008 Claxton Shield.

In 2005, Kingman coached the Under 16s NSW Squad at the National Championships in Mount Gambier, leading them to a first-place finish.

In the Sydney Blue Sox inaugural Australian Baseball League season, Kingman played four games going 5 for 11.

Kingman did not play again until he was activated as a pitcher at the age of 44 at the end of the 2017–18 Australian Baseball League season where he pitched the final inning in relief, retiring all three batters he faced.