The oil is gone from Rayong's Mae Ram Phueng Beach but now idyllic Koh Samet is under threat.
Natural Resources and Environment Varawut Silpa-archa said the oil-spill cleanup went quickly at on the Muang District beach.
Satellite images from Sunday morning showed no signs of oil on Mae Ram Phueng Beach or in the sea close to Khao Laem Ya-Moo Koh Samet National Park, but that may change.
Varawut said oil-stained sand was removed, the normal condition of the beach was restored and officials would be watching for the remaining oil slicks that were moving towards Ao Phrao Bay at Koh Samet.
Mae Ram Phueng Beach was safe as winds were blowing oil slicks to the east, but they were moving toward
Officials planned to lay containment booms at a 500-meter-wide channel to protect the coastline of Rayong.
Varawut asked provincial authorities to suspend local fishing for about a month and give assistance to affected people. He said Star Petroleum Refining Plc., the owner of the undersea oil pipeline that leaked crude oil last week, would be sued for damage to marine resources.
The Pollution Control Department would report the quality of seawater until situations returned to normal, Varawut said.