BANGKOK - Thai oil and gas firm, PTT Exploration and Production Pcl said on Monday it would buy Partex Holding B.V. from Libson-based Calouste Gulbenkian Foundation for $622 million, its latest acquisition of upstream and midstream assets.

The move will immediately increase the company's revenue stream, production and reserves, PTTEP Chief Executive Phongsthorn Thavisin said in a statement, adding the investment aligns with the company's strategy of focusing on prolific areas such as the Middle East and developing relationships with local government for future investments in the region.

"This transaction marks a reconfiguration of the foundation's asset base, which has as its main objective to achieve long-term attractive returns," Isabel Mota, chair of the foundation's board of directors said, in a statement.

The Calouste Gulbenkian Foundation is a private philanthropic entity, which finances arts, education and science.

In March, PTTEP, a unit of the state-owned PTT Pcl, bought Murphy Oil Corp's assets in Malaysia for $2.13 billion.

Partex will add sales of 16,000 barrels of oil equivalent per day (boed) from stakes of oil and gas projects in Oman, the United Arab Emirates (UAE) and Kazakhstan, PTTEP said.

The deal will also add proved and probable reserves of approximately 65 million barrels of oil equivalent according to PTTEP's working interest.

This acquisition "allows us to create new business partnership with both national oil companies of Oman and UAE," Phongsthorn added.

The deal is expected to close in the fourth quarter of 2019.

PTTEP reported an average sales volume of 319,230 boed in the three months ending in March.

(Reporting by Chayut Setboonsarng in Bangkok; and by Catarina Demony and Patricia Vicente Rua in Lisbon; editing by David Evans) ((chayut.setboonsarng@tr.com; +66854849033; Reuters Messaging: chayut.setboonsarng.thomsonreuters.com@reuters.net))