SURAT THANI: An earthquake, measuring 2.4 on the Richter scale, struck Koh Samui at 8.24am on Thursday.
Jirawat Kamchadphai, a meteorologist at the Earthquake Observation Division, said the quake happened in tambon Ang Thong on the western part of the island.
The epicentre of the tremor occurred at a depth of four kilometres under Thaweerat Phakde, 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 (KMFZ), a major active strike-slip fault system in southern Thailand.
Some people sent messages to the division's website, reporting that they felt two vibrations resembling explosions.
The Department of Mineral Resources said the quake was caused by the geothermal energy.