Before the race in Norway on Friday night, his coach, Thabo Matebedi, challenged him to finally break his previous personal best of 19.77 and consistently run under 20 seconds.
Dambile responded in the best possible way, producing a superb performance to win the race and set a new PB.
Zimbabwe's Makanakaishe Charamba finished second with a personal best of 19.88, while Dominican Republic's Alexander Ogando took third in a season's best 19.96, with all three athletes dipping below the 20-second mark.
The 24-year-old will now return to Tshwane to reunite with his coach as preparations begin for a busy second half of the season, including the Ultimate Championships in Budapest, the Commonwealth Games in Glasgow and more Diamond League meetings.
Dambile has enjoyed an impressive season, and he first broke the 20-second barrier in April when he won the Kip Keino Classic in Nairobi in 19.77, and his latest performance shows he is becoming the consistent sub-20-second runner his coach has been demanding him to be.
His season did not begin well after an injury forced him to miss the World Athletics Relays in Botswana.
However, he has made an unbelievable comeback and is now producing the best performances of his career.
Coach Matebedi has praised Dambile's talent, describing him as the best athlete he has coached since former World Championships 200m bronze medallist Anaso Jobodwana, who has since retired from the sport.
Earlier this week, he also set a new South African 150m record of 14.78 at the Ostrava Golden Spike meeting, finishing second behind American superstar Noah Lyles, who broke the world record with a 14.67.
Meanwhile, former world indoor 800m champion and Olympic finalist Prudence Sekgodiso narrowly missed out on a podium finish in the women's 800m.
She finished fourth in 1:58.61, just outside the top three after targeting a podium place.