UPDATE 1-Norway's Golar, Thai PTTEP in Australian gas deal

* Final investment decision seen in 2010, on stream in 2013

* Investment "hundreds of millions of dollars" - Golar

* 50:50 between the companies

(Adds comments from Golar, share price)

OSLO, July 9 (Reuters) - Norwegian gas shipper Golar LNG (GOL.OL) and Thai energy firm PTT Exploration and Production PTTE.BK have entered into an agreement to jointly develop an gas project in North West Australia, Golar said on Thursday.

A memorandum of understanding to develop floating liquefied natural gas production (FLNG) and invest in projects worldwide was signed by the two companies in August last year.

Golar told Reuters that a final investment decision would not come until 2010, and hinges on the successful outcome of an engineering and design study.

"It's early days yet, but the project could come on stream in 2013. We would aim to produce 1-1.5 million tons of LNG per year," Chief Financial Officer Graham Robjohns said.

"The investment would be in the hundreds of millions of dollars. That's considerable, but we believe it would be highly profitable as well," Robjohns said.

The two companies will build a floating plant by the gas resources which will transform natural gas to liquid, from where it can be loaded to vessels and transported to markets.

Golar said it would buy a stake in the gas resource and that the two companies would share the development cost.

"We would take a 50 percent stake in the gas, invest in the plant on a 50/50 basis and then share the gas offtake from production 50/50," Robjohns said.

Golar recently announced its intention to restructure the company and form a subsidiary company that would focus on project development, both floating storage and regasification (FSRU) projects, as well as liquefaction projects.

"In due course the new company will likely raise additional capital and will seek a separate listing," Golar said in a statement.

Shares in Golar fell 4.7 percent to 50.50 crowns at 1016 GMT against a 1.6 percent rise in the main index at Oslo bourse .OSEBX.

(Reporting by Aasa Christine Stoltz and Terje Solsvik; Editing by David Cowell and Simon Jessop)