The ICC said match officials reported concerns about the legality of the off-spinner's action during his ODI debut in Cairns on Tuesday where he took 1-46 in the Proteas' 98-run win.
Subrayen must undergo an independent assessment of his action at an ICC-accredited testing facility within 14 days.
He can continue bowling until the results of his test are known.
Bowlers are permitted 15 degrees of elbow extension while delivering the ball.
Reuters contacted Cricket South Africa for comment.
The 31-year-old Subrayen has a record of bowling illegally in domestic and T20 cricket.
He was suspended from bowling in domestic cricket in late-2015 after failing an assessment but was cleared to resume after another test a few months later.
He was also suspended in late-2012 over his action but cleared to bowl again in early-2013 after remedial work.
Subrayen made his test cricket debut last month against Zimbabwe in Bulawayo, picking up four first-innings wickets.
