South Africa A spinner Senuran Muthusamy helped skittle Sri Lanka A for 151 in their second innings on day three of the four-day match in Pallekele.
Muthusamy took 5-53 in 16.4 overs on Wednesday to go with his first-innings figures of 7-123.
Pace bowlers Lizaad Williams and Gerald Coetzee picked up two wickets each, and 17-year-old first-class debutant Kwena Maphaka one.
Ramesh Mendis top-scored with 46 as the hosts set SA A a daunting target of 346 to win.
The visitors were bowled out for 131 in their first innings.
