South Africa captain Faf du Plessis and Temba Bavuma both made half centuries as they increased their lead over Bangladesh to 379 runs at lunch on the fourth day of the first test on Sunday.
The home side were 203 for three wickets at Senwes Park after the opening session as Du Plessis led an aggressive push for runs with 149 added to their overnight total at a rate of 4.5 per over.
South Africa are looking to set Bangladesh a mammoth target but also need to declare early enough to give themselves sufficient time to bowl out the opposition on a flat, lifeless track.
Du Plessis was 77 not out off 92 balls while Bavuma was unbeaten on 64. South Africa were 54-2 overnight with Hashim Amla on 17 and Bavuma on three.
Amla was the only wicket to fall before lunch as he was caught behind for 28.