Left-arm fast bowler Little and wicketkeeper Tucker earned their spots after impressive performances in the Under-19 World Cup in Bangladesh earlier this year. Little picked up four wickets in five matches in that tournament, including 3 for 52
against eventual runners-up India in their first game. Tucker was
Ireland's top run-scorer in the competition, with 222 runs in six games at an average of 44.40.
"We wanted to bring some freshness to the squad," chairman of selectors Alan Lewis said. "Left-arm quicks have been hugely successful in T20s and Josh's introduction will drive his career forward, we hope. He bowls with pace and is an excellent athlete.
"Lorcan's ability to score all around the ground with his 360-degree game - as witnessed at the U19 World Cup - coupled with his wicketkeeping gives us excellent balance."
Allrounder Thompson, who was Ireland's youngest player at 16, last played an international game in 2008, but was recalled after stellar performances in the domestic circuit this year.
"Clearing the ropes and strike rates which are vital in this format have proved difficult for us recently but we hope with the re-introduction of the quartet, added to our experience that we can build a new identity to the way we play," Lewis said.
Ireland are scheduled to host Hong Kong for two T20Is in Bready on September 5 and 6.
Ireland squad: William Porterfield (capt), Peter Chase, George Dockrell, Joshua Little, Andrew McBrine, Barry McCarthy, Kevin O'Brien, David Rankin, James Shannon, Sean Terry, Greg Thompson, Lorcan Tucker (wk), Craig Young