Smith, who has accumulated over 50 caps for the Stormers, is the latest player to join the expanded squad, after his provincial team-mate Ruben van Heerden joined the group last week in preparation for the double-header in Gqeberha.
He will report for duty with the rest of the squad in Johannesburg on Sunday, where they will resume their preparations from Monday after spending the weekend with their families.
Teammate Salmaan Moerat was forced out of the group after suffering another long-term injury, while emerging Boks Ruan Nortje and Cobus Wiese are away with the Bulls in Ireland. However, coach Rassie Erasmus confirmed that stalwarts Eben Etzebeth and Lood de Jager are good to go, as is Junior Springbok captain Riley Norton.
The squad will depart for the Eastern Cape on Wednesday afternoon, with the Springbok and SA 'A' teams having their respective captains' runs on Friday for Saturday's clashes at the Nelson Mandela Bay Stadium.
Springbok coach Rassie Erasmus and SA 'A' team head coach Mzwandile Stick will announce their matchday squads on Tuesday.
Springbok loose forward Jean-Luc du Preez has firmly dismissed reports in France suggesting he is on the verge of retirement due to ongoing concussion-related issues.
Former Springboks coach Nick Mallett believes Stormers scrum-half Imad Khan has done enough with his recent performances to emerge as a surprise contender for national selection.
Players running out for the South Africa 'A' against Zimbabwe will forever be tied to the Republic unless they have parents or grandparents born in another nation.
Stormers director of rugby John Dobson has confirmed that the Cape Town side will not sign veteran Argentina lock Tomas Lavanini, and will instead back home-grown talent.
