The 2018 World Cup quarter-finalists hardly missed the injured star striking duo of Luis Suarez and Edinson Cavani as they made it seven goals in two games.
Uruguay, comfortable 3-0 victors over Uzbekistan on Friday in the four-team tournament, profited from some poor Thailand defending in the Chinese city of Nanning.
Unmarked Inter Milan midfielder Matias Vecino headed home after just six minutes -- Thai goalkeeper Siwarak Tedsungnoen should have done better -- and it was 2-0 on 38 minutes when Gaston Pereiro prodded in after the Thai defence went AWOL.
Stuani, starting because of the absence of PSG's Cavani and Barcelona's Suarez, made it 3-0 just before the hour with a close-range bullet header from a corner.
The Girona striker, who scored a brace against the Uzbeks, had hit the post just minutes earlier.
Substitute Maxi Gomez made it 4-0 two minutes from the end of normal time with goalkeeper Siwarak stranded out of position.
Earlier in the day, Uzbekistan defeated Fabio Cannavaro's China 1-0 to leave the hosts last of the four teams involved.