Kewell overlooked for World Cup qualifiers
Osieck named a 23-man party for the match against the Thais on September 2 in Brisbane and away to the Saudis four days later.
"From my point of view, it's the strongest group we have at the moment," Osieck told reporters.
Kewell missed the friendly victory over Wales in Cardiff earlier this month because of a lack of fitness having been without a club since leaving Turkish side Galatasaray at the end of last season.
Although he signed for Melbourne on Saturday, Kewell is not anticipated to move to Australia until next month with Osieck expecting the former Liverpool forward to rejoin the squad soon.
"He definitely is healthy but, to be psychically healthy and match fit, it's always a gap," Osieck said.
"I cannot give you an update on his match fitness. I simply know Victory will expect him early September to join team training."
Australia, runners-up in the Asian Cup in January, must finish in the top two of the group that also features Oman to advance to the next stage.
Squad: Tim Cahill, Nathan Coe, Luke DeVere , Brett Emerton, Adam Federici, Brett Holman, Mile Jedinak, Josh Kennedy, Neil Kilkenny, Robbie Kruse, Scott McDonald, Matt McKay, Mark Milligan, Lucas Neill, Sasa Ognenovski, Adam Sarota, Mark Schwarzer, Matthew Spiranovic, James Troisi, Carl Valeri, Luke Wilkshire, Rhys Williams, Michael Zullo.