The Provincial Electricity Authority has apologised to people on Koh Samui and Koh Phangan after a three-day blackout on the islands ended yesterday.
An official apology will be published and announced through the media, PEA deputy governor Damrongsak Tanrattanakun said.
His statement came after engineers managed to restore electricity on the two resort islands early yesterday.
They were able to connect the damaged part of an underground high-voltage cable at 1.15am yesterday before re-starting the distribution of electricity at 4am, ending three days of chaos.
Many residents struggled to carry out their daily lives and tourists were leaving the islands in droves.
Petrol had to be brought in from the mainland to feed the power generators which kept some of the island's important infrastructure facilities functioning.
Thanongsak Somwong, chairman of Koh Samui's tourism promotion association, yesterday breathed a sigh of relief that the power outage was over.
He said the problem must not recur as it had brought the islands, which are two of the country's top tourist destinations, to their knees.
The private sector will "not forgive" the authorities if there is another massive blackout, he said.
"Koh Samui is the face of the nation," he said.
Mr Thanongsak called on the government to have enough mobile power generators on standby for the islands in case of future emergencies.
The two islands have experienced growing demand for power over the past 15 years due to tourism growth, Mr Damrongsak said.
The latest outage is believed to be the result of high usage of electricity, with December marking the start of the high season for the islands, PEA deputy governor Numchai Lowattanatakul said.
Mr Thanongsak said the urgent mission for tourism operators and the government is to restore tourists' confidence.