Both players are missing the current one-day international series against Bangladesh due to injuries.
Jayawardene is recovering from a back injury and Thirimanne from an ankle problem.
Uncapped all-rounder Chaturanga de Silva was named as standby for left-arm spinner Rangana Herath who has a knee injury.
The selectors retained 11 of the players who played in the last World Twenty20 hosted by Sri Lanka two years ago.
Sri Lanka lost in the final to West Indies by 36 runs.
Squad: Dinesh Chandimal (Captain), Lasith Malinga, Tillakaratne Dilshan, Kusal Perera, Kumar Sangakkara, Mahela Jayawardene, Lahiru Thirimanne, Angelo Mathews, Thisara Perera, Nuwan Kulasekara, Suranga Lakmal, Rangana Herath/Chathuranga de Silva, Sachithra Senanayake, Ajantha Mendis, Seekuge Prasanna.
(Editing by Ed Osmond)
