May 2 (Reuters) - Singapore's Olam Agri Holdings said on Thursday it was planning to make an off-market bid for Australia's Namoi Cotton for A$136.6 million ($89.13 million), which would be subject to the suitor acquiring at least a 50.1% stake in the target firm.

The new bid comes just a few months after Global commodity merchant Louis Dreyfus Company (LDC) first made a cash offer to acquire the 83% of issued shares in Namoi that it does not already control.

Under the new bid, Olam's offer price would be A$0.66 per share, higher than the Dreyfus' A$0.60 rival offer.

Olam Agri, a unit of agri-business firm Olam Group , said it would propose to increase the value of its offer to A$0.70 per share if it obtains a 90% stake of Namoi before the offer period ends.

The off-market offer differs from Olam's takeover offer structure as it was originally proposed under Olam’s non-binding indicative offer early this year, Olam said, adding that the off-market bid is to provide simplicity and certainty for Namoi shareholders.

"Olam has successfully completed its confirmatory due diligence and is pleased to formalize its intention to acquire Namoi's shares," CEO Sunny Verghese said in a statement.

($1 = 1.5326 Australian dollars) (Reporting by Poonam Behura in Bengaluru; Editing by Anil D'Silva and Alan Barona)