* To buy stake in U.S.-based bioplastic maker this month - sources
* NatureWorks seen as a potential seller
By Pisit Changplayngam
BANGKOK, Sept 13 (Reuters) - Thailand's largest olefins maker, PTT Chemical Pcl , will acquire a stake in a U.S. bioplastic polylactic acid (PLA) maker as part of a foreign expansion drive, a source at Thailand's Energy Ministry said on Tuesday.
"They are in talks with the seller and therefore the portion (of the stake) cannot be disclosed," the source, who declined to be identified, told Reuters. "That being said, the deal is close to being finalised this month," he said, adding that the seller plans to build a new U.S. bio-plastic plant.
Another source at its parent company, state-controlled PTT Pcl , said NatureWorks LLC, owned by U.S.-based agribusiness giant Cargill Inc , is a potential seller.
Nebraska-based NatureWorks is the world's largest polylactic acid manufacturer.
"With this stake purchase, it would allow PTT Chemical to just import PLA to use directly and not have to waste time building a new plant, which could take up at least three years," he said.
PTT Chemical declined to comment.
PTT Group has been expanding into bioplastics with demand for bioplastic polylactic acid rising globally. Thailand only imports bioplastic polylactic acid.
In July, PTT joined with Japan's Mitsubishi Chemical Holdings Corp to form a joint venture, PTT MCC Biochem Co Ltd, to build a bio plastic pellet plant worth 7 billion baht ($232 million).
PTT Chemical has capacity for 2.88 million tonnes of olefins products a year and is in the process of merging with another PTT affiliate, PTT Aromatics and Refining Pcl , expected to be competed in October.
Once completed, it would create Southeast Asia's second-biggest petrochemicals firm by market value after Malaysia's Petronas Chemical and the merged firm will be named PTT Global Chemical Pcl.
At 0809 GMT, PTT Chemical shares were down 0.8 percent, while the broader market was 0.6 percent lower.