At the time of Stumps, Pakistan's score read 221/5, trailing Sri Lanka by 91 runs with Saud Shakeel (69) and Agha Salman (61) standing unbeaten at the crease.
Pakistan's Fakhar Zaman has been voted the ICC Men's Player of the Month after a stunning month in April. Prabath Jayasuriya and Mark Chapman were also in the race but Fakhar emerged as the most promising of all.
The host team won all two games of the series at Galle 2-0, winning its 100th Test match and leaving the visitor still searching for their first triumph in cricket's longest format.
Sri Lanka spinner Prabath Jayasuriya broke a 71-year-old record when he dismissed Ireland's Paul Stirling to claim his 50th Test wicket on the final day of the second Test in Galle on Friday.
Karunaratne, who had made 179 in the first Test at the same venue last week, stitched a 228-run opening stand with Nishan Madushka and made his 16th Test hundred in the process
Unbeaten centuries from Dinesh Chandimal and Sadeera Samarawickrama after Dimuth Karunaratne and Kusal Mendis' good knocks had given Sri Lanka a big total on day two