Frosler (23) and Ngcobo (21) both started in Chiefs 3-0 defeat against Al Ahly in the CAF Champions League final on Saturday and moved swiftly from Casablanca to report for national duty in Japan.
Both players hold extensive experience for the nation at various junior levels in the national team and are expected to play crucial roles in David Notoane's squad that has been weakened by various factors over the past month.
Many of the European contingents including overaged players like Percy Tau was denied an opportunity to be called up by their club sides - while five players were withdrawn due to 'medical reasons.
"We have had a very long trip and are still a bit disappointed at the weekend's results, however as professionals we are now settled in Tokyo and will be 100 percent ready to play if we are selected in the opening match," Frosler said.
South Africa U23 open their campaign against tournament hosts Japan on Thursday afternoon at the Ajinomoto Stadium in Chofu before taking on France and Mexico in the rest of their Group A fixtures.