An earthquake, measuring 2.4 on the Richter scale, struck Koh Samui at 8.24am on Thursday.
A meteorologist at the Earthquake Observation Division said the quake happened on the western part of the island.
The epicentre was at a depth of four kilometres under a loop road around the island.
It was the first quake detected by the division in the Gulf of Thailand, he said.
Since 2008, there have been 16 earthquakes in Surat Thani. Most occurred on and near the Khlong Marui Fault Zone in southern Thailand.
Some people sent messages to the division's website, reporting that they felt two vibrations resembling explosions.
