Sri Lanka assumed complete control of the second Test in Colombo as another shoddy batting display left South Africa facing the prospect of a heavy defeat and a 2-0 series loss.

Having been rolled out for 126 and 73 en route to a 278-run hammering in the first Test in Galle last week, the Proteas surrendered meekly to 124 all out in reply to the hosts' 338 on Saturday's second day in the capital.

Akila Dananjaya (5-52) and Dilruwan Perera (4-40) were the tormentors-in-chief, while captain Faf du Plessis' counter-punching 48 from 51 balls provided the only evidence of resistance as the tourists lost their final five wickets for just 10 runs in the space of 27 deliveries.

Despite clearly having the measure of a batting line-up bereft of confidence and conviction, Sri Lanka opted against enforcing the follow-on and reached stumps on 151-3, a mammoth lead of 365 - already more than South Africa have amassed in their three innings combined in this series.

Danushka Gunathilaka thumped two maximums in his 61 from only 68 balls, while the in-form Dimuth Karunaratne followed up his prior scores of 158, 60 and 53 with an unbeaten 59, taking his own personal tally beyond that of his beleaguered opponents as a collective.

The tone for South Africa's torrid day was set by Sri Lanka's last-wicket pair Dananjaya (43 not out) and Rangana Herath (35), who hung around for 18 overs adding a further 61, before Keshav Maharaj dismissed the latter to finish with 9-129.

And the writing was on the wall inside nine overs of the reply as the Proteas fell to 15-3 - Dean Elgar, Theunis de Bruyn and Aiden Markram all departing cheaply.

Du Plessis decided attack was the best form of defence, taking Dananjaya for three consecutive fours at the end of the first over following lunch, and crunching Herath over long-off for six in the next.

But a 50 stand was ended when Hashim Amla - dropped on two as he passed 9,000 Test runs - perished in familiar circumstances, offering a catch to a close fielder on the leg side from Dilruwan, as he had in both innings in Galle.

Du Plessis was next to fall, getting a faint under edge behind in trying to sweep Dilruwan, who, along with Dananjaya, ran through the tail in ruthless fashion.

After tea, Gunathilaka and Karunaratne made hay - the former eventually holing out off Maharaj, who also picked up Dhananjaya de Silva lbw, but even the run out of Kusal Mendis did not raise much of a smile on South African faces at the end of another day of toil.