A senior Immigration Ministry official said Wednesday the verdicts had been issued a day earlier in Kawthuang, a town on Myanmar's southern tip.
The official declined to be identified because he was unauthorized to speak to the media.
Thailand's Foreign Ministry confirmed the verdicts, but made no immediate comment.
The Thais were arrested during a military operation in early July for illegally entering the country and attempting to grow rubber crops on 1,500 acres of land.
So far the case has not affected bilateral relations. Last week, Myanmar's president ended a three-day visit with an agreement to boost economic cooperation between the two neighbors.