The leak from a pipeline owned by Star Petroleum Refining Public Company Limited (SPRC) started late on Tuesday and was brought under control a day later after spilling an estimated 50,000 litres of oil into the ocean 20km from Thailand’s east coast.

A 47sqkm area of the sea has been impacted and oil slick drifted close to Rayong’s coastline on Friday, a satellite image from the government’s Geo-Informatics and Space Technology Development Agency (GISTDA) showed.

The navy, which is working to contain the spill at sea, said it may take over a month to restore beach areas affected.

SPRC workers on Friday unfurled long inflatable oil boom barriers near the tide line, designed to try and keep the slick from spoiling the tropical beaches.

Authorities have previously warned the spill could impact the nearby Khao Lam Ya National Park, home to exotic coral reefs and sealife.

The Thai government has filed an official complaint to seek compensation for the damages the oil spill has caused, deputy transport minister Atirat Ratanasate told reporters on Friday.

In 2013, an oil spill from another undersea pipeline blackened beaches in Rayong and caused environmental damage that took months to restore, impacting fishing and local tourism.