Shattered taekwondoin Safwan Khalil's third Olympics has ended in just six minutes, with an opening loss to Ramnarong Sawekwiharee underlining the brutal equation for some Australian athletes in Tokyo.

Thai fighter Sawekwiharee landed repeated blows to the body throughout all three rounds of the round-of-16 bout, winning 23-7.

Sawekwiharee's defeat in his ensuing quarter-final, against second seed Vito Dell'Aquila, ended Khalil's hopes of a second chance in the men's 58kg tournament.

Khalil, who lost a bronze-medal fight at London 2012, loomed as arguably Australia's best chance of securing a first Olympic medal in the sport since Lauren Burns in Sydney 2000.

When the Games were postponed, the veteran put his life on hold for a further year to continue training and become the first man to represent Australia in taekwondo at three Olympics.

But the 35-year-old will now board a flight home as soon as possible, as per biosecurity protocols, and spend a fortnight in hotel quarantine.

"I am very devastated right now and confused," Khalil said.

"It just wasn't the way I expected the fight to go.

"That wasn't good at all."

Khalil, who is one of seven brothers, was eight months old when his family fled to Australia while escaping Lebanon's civil war.

Khalil quipped that his older sibling and coach Ali Khalil wouldn't "say anything" about the bout.

"He'll just hit me," he said.

"Ali is the national coach now but the others have stopped competing, they just shout and scream at me.

"They were all coming to shout and scream at me here pre-COVID but I'm glad they didn't after that performance."

A gam-jeom handed Khalil an early 1-0 lead, while he took a 4-2 lead thanks to a kick to the head before Sawekwiharee dominated.

Stacey Hymer, who faces Canadian Skylar Park on Sunday in the women's 57kg competition, is the next Australian taekwondoin fighting in Tokyo.