A Bangkok Airways ATR 72-500 has skidded off the runway while landing at Koh Samui airport and crashed into a control tower.
There are unconfirmed reports of fatalities among those on board.
The aircraft has the Thai registration HS-PGL, says an airline official.
It was on its way from the resort town of Krabi and trying to land in rainy weather around 14:00 when the incident happened, adds the official.
She was unable to say if there were any injuries or fatalities, adding that the airline will issue a statement shortly.
Thai news reports suggest that there were injuries and fatalities, and most of those on board were tourists.