Ngobeni started training with Ea Lla Koto on Wednesday, having played 29 games for the club on loan last season.
Sundowns coach Pitso Mosimane recently confirmed Ngobeni would be heading to to Stars at the player's request.
The 28-year-old keeper is yet to play this campaign, as he provided cover to Denis Onyango, Kennedy Mweene and Razak Brimah at Chloorkop.
Ngobeni initially joined the Brazilians as a free agent in February 2013 after parting ways with Kaizer Chiefs.
Stars are also close to adding 25-year-old Belgian striker Maxime Cosse to their roster.