In the Australian Women's Amateur over the same layout it will be Queenslander Karis Davidson, from the Sanctuary Cove Golf Club, who will tackle the defending champion Minjee Lee from the Royal Fremantle Golf Club near Perth.
19 year old Koh, from the Maunkau Golf Club in Auckland eliminated American Max Buckley in his morning quarter final match up before surviving a tense semi final battle against local golfer and two time Australian Boy Champion Anthony Murdaca in the afternoon.
He will endeavour to become the first New Zealander to win the Australian Amateur Championship since Michael Campbell did so 22 years ago.
Cottesloe Golf Club's teenager, Curtis Luck, continues his recent good form which included a victory at the Victorian Junior Masters but this is clearly a significant rise in grade. He defeated American
David Snyder 2 up at the final hole in the morning semi final before tackling and defeating Victorian Todd Sinnott again at the final hole this afternoon.
Davidson recorded a comfortable victory over New Zealander Chantelle Cassidy in her morning quarter final before defeating South Australia's Jenny Lee at the second extra hole in the semi.
Minjee Lee had an easy win over her fellow West Australian Jayde Panos in the morning match before defeating Luna Sobron of Spain in a much more tightly fought semi 2&1.
It was hard luck for the two South Australians looking to make the final, Lee and Murdaca, as a local flavour would no doubt have added to the intrigue tomorrow.