BANGKOK - Crude oil that leaked from a pipeline in the Gulf of Thailand over the weekend has reached a Thai tourist resort, pipeline operator PTT Global Chemical Pcl said on Monday.

Thai soldiers in white biohazard suits take part in a clean-up operation at Ao Prao Beach on Koh Samet, Rayong July 30, 2013.[Photo/Agencies]

Around 50,000 litres of crude oil poured into the sea on Saturday around 20 km (12 miles) off the coast of Rayong, southeast of the capital Bangkok.

"An oil slick has reached Ao Prao beach on Koh Samet island," PTT Global, which estimates that around 5,000 litres remain to be cleaned up, said in a statement.

"This should be the last oil slick that will come to shore. It is stuck in one particular corner of the shore close to some rocks."

Koh Samet, known for its white sandy beaches, is thronged by local and foreign tourists, thanks to its proximity to Bangkok, and is home to several high-end and budget resorts.

About 200 soldiers have been deployed to help clean up the spill and 300 more will provide back-up, Wichit Chartpaisit, governor of Rayong province, told Reuters, adding that the task would take some time, although he gave no details of how much.

PTT Global Chemical Pcl is part of state-controlled PTT Pcl, Thailand's biggest energy firm.

Another subsidiary, PTT Exploration and Production Pcl, was involved in Australia's worst offshore drilling accident in 2009, when thousands of gallons of crude oil spewed into the sea after a damaged oil well blew up.

The slick from the Montara oil field off Australia's northwest coast spread as far as Indonesian waters. An Australian government inquiry blamed the spill on systemic shortcomings at the Thai oil giant.