KTM riders hogged the podium at Horsham with Australian Dylan Leary finishing the day runner-up to Lamont and cementing his spot at third in the series standings.
Lamont won the opening two races of the day at Horsham, before clinching the overall class win for the weekend with a third in the final race.
"I'm really happy to win the round and extend my lead in the series," said Lamont, who qualified only 10th, satisfied to complete just a couple of laps of qualifying to secure a reasonable spot with the minimum of fuss or risk.
But he certainly turned it on for the racing proper, leading the first two races from start to finish before settling for a solid third in the last race to secure the overall result.
"I'm feeling very good, fresh and fast at the moment," said Lamont. "I put in the hard yards in the first two races and was happy to accept third in the last one ... job done. There is no point trying too hard to win all three races and risk crashing.
"I really need to thank everybody who has helped me - the CMR Red Bull KTM team, Jeff Leisk of KTM in Australia, Cannon Smith and Patrick Stafford of KTM in New Zealand, trainer John Appel, Dragon Goggles, Shift apparel and BikesportNZ.com for all their support.
"The track was a bit of a bog hole in places but the club did a really good job of the track considering the conditions and it was definitely a good weekend for me."
Meanwhile, another New Zealander, Motueka's Josh Coppins, continues to lead the MX1 open class in Australia. Coppins (Yamaha) finished 3-4-1 in his three outings at Horsham and was forced to accept the third step on the podium for that day, but he remains the man to beat overall, leading the series standings by eight points from Australian Suzuki rider Todd Waters.
Another Kiwi, Mount Maunganui's Cody Cooper (Suzuki), finished second overall at Horsham, clocking 2-1-3 results, and is now fifth in the championship standings.
The Australian Motocross Championship series will continue at Appin, near Sydney, in New South Wales this Sunday and the New Zealand riders are planning to again be among the frontrunners.