The quake occurred at 4:17am about 70 kilometres west of Prachuap Khiri Khan and was felt throughout the province in Muang, Hua Hin, Kui Buri and Pranburi districts.

The tremor was felt in Phetchaburi and Ratchaburi provinces as well, the Meteorological Department said.

It was the sixth and most powerful quake felt in the province since September 28, when the first earthquake measuring 4.8 on the Richter scale in the past 50 years was registered.

National Disaster Warning Centre chairman Smith Thammasaroj said the quake was triggered by a Ranong fault line that geologists believe became active in the latest tsunami. The quake did not cause intense effects in Thailand, with its epicentre 70-80 km away in Burma; however, officers have been inspecting two dams in Kanchanaburi. The Srinakharin and Vajiralongkorn dams have drawn concern following the moderately powerful quake due to their location near the fault line.

The quake might have affected Bangkok had it reached 8 on the Richter scale, Smith said.

Tiva Supachanya, director of the Thai Habitation Institution in Prachuap Khiri Khan, said the province has been affected by quakes centred in Burma since ancient times, and they have never caused severe disaster in Thailand.

Prachuap Khiri Khan governor Kittipong Sunanan said although the quake was intensely felt, no severe damage has been reported so far. He ordered district-chief officers to meet with hotel and condominium operators to inspect the safety of their buildings, which might face engineering problems due to the quake. Provincial officers have been preparing measures to alert citizens and tourists in case of disaster.

The quake alarmed tourists and those staying in tall buildings. Prasert Chaiyasirisuwan, a businessman living on the eighth floor of a condominium in Hua Hin, was frightened by the quake's intensity.

"It was the sixth quake within 12 days. If there are more quakes, I must look for a new residence," he said.

The quake caused cracks at a monastery and a Buddhist image at Wat Tanote Luang in Phetchaburi's Cha-am. The temple sits just 200 metres from the shore.

Some locals have begun to worry about a potential tsunami, but provincial meteorological officers insist this would not happen in the Gulf of Thailand.