Koh Samet off Rayong province is threatened by the oil slick, which gushed from an undersea pipe in the Gulf of Thailand earlier this week.
On Friday, the oil began washing up on Rayong’s largest beach, the 12-kilometre-long Mae Ram Phueng, which was declared a disaster zone.
A massive clean-up operation has seen more than 500 officials collect about 15,000 litres of spilled oil in barrels, leaving about 1,000 litres still to clean up, said local reports on Sunday.
However, satellite images of tidal conditions show the oil slick heading to Koh Samet’s Ao Prao Bay – a popular beach resort area rich in corals and seagrass.
Leading the battle to prevent the slick from reaching Samet are three agencies – the Pollution Control Department, Department of Marine and Coastal Resources and Department of National Parks, Wildlife and Plant Conservation.
Natural Resources and Environment Minister Varawut Silpa-archa will issue instructions to tackle the spill after surveying the area on Sunday afternoon, said reports.