They're facing a powerhouse of under-23 football in Asia, but Arnold is confident the Olyroos can end Australia's 12-year Olympic football drought.

Australia take on South Korea in Bangkok on Wednesday (0015 Thursday AEDT) in the semi-finals of the AFC Under-23 Championship.

A win will be enough to secure Arnold's team a place at this year's Olympics in Tokyo.

Overcoming the Koreans will be far from simple however with the 2012 Olympic bronze medallists the only team to reach the semi-finals with a perfect record.

Kim Hak-bum's side defeated Iraq 2-1 in the quarter-finals on Sunday to make it four semi-final appearances from four AFC U-23 tournaments for the Koreans.

Arnold's team has faced South Korea twice in the past year, both games ending in draws, and while aware of their opponents' strengths, the Australian coach says they also know exactly what to expect.

"We played against them in Cambodia, drew 2-2, we played against them in Malaysia only a couple of weeks ago and drew one-all. We know what they're about," Arnold said.

"A lot of their players that are here, a few of them are with the senior national team and a lot of them are playing in a top league in the K-League.

"That's probably what makes them a little bit different to us but once we go on the pitch we'll be ready."

Arnold is expected to make several changes to his starting XI following Saturday's exhausting extra-time 1-0 quarter-final win over Syria.

Match-winner Al Hassan Toure could be a chance to start up front while Melbourne City's Denis Genreau, who has missed the past two matches due to an ankle injury, is understood to be in the frame for a return.

Australia's Olympic dream won't end if they lose to the South Koreans, with a win in the third-placed playoff against the loser from the other semi-final between Uzbekistan and Saudi Arabia also guaranteed a berth in Tokyo.

But Arnold says his team is eager to get the job done and dusted at the Thammasat Stadium.

"All we're doing is talking about that at the moment, building the players' belief and confidence and making sure they're fresh and ready to go."