The Proteas have qualified directly for the 50-over World Cup to be played in India later this year after the first ODI between Ireland and Bangladesh was abandoned.
Mushfiqur Rahim hit an unbeaten half-century as Bangladesh secured a seven-wicket win over Ireland on day four of the one-off Test match in Dhaka on Friday.
Ireland's top order folded in quick time on the second evening of their Test against Bangladesh, leaving an uphill battle for the visitors.
A fine half-century from captain Paul Stirling helped Ireland coast to a seven-wicket victory over Bangladesh in their final T20 international in Chittagong.
Bangladesh captain Shakib Al Hasan took five wickets as Ireland were beaten by 77 runs in their second T20 international in Chattogram, giving the hosts an unassailable 2-0 series lead.
Ireland suffered defeat in their first T20 international against Bangladesh after falling to a 22-run defeat on the Duckworth-Lewis-Stern (DLS) method in Chattogram.