April 21 (Reuters) - Rite Aid Corp said on Thursday it had rejected a buyout proposal from private-equity firm Spear Point Capital Management, which valued the drugstore chain at about $3.6 billion, including debt.

Rite Aid's board said the proposal was not credible as it had no evidence of financing and required multiple months of exclusivity, among other reasons.

Spear Point said it had also offered to enlist the services of its data valuation and monetization partner, Silverback United, to value Rite Aid when it presented the bid, and also offered to share the valuation with the drugstore chain so it can seek a higher value.

However, as Rite Aid rejected the offer, Spear Point said it plans to discuss with the company's shareholders and management about how Rite Aid is "significantly undervalued and explore management's inability to unlock that value."

Shares in Rite Aid closed 6% lower at $7.68 on Thursday.

The New York Post had reported late on Wednesday the private-equity firm had made an offer valuing Rite Aid at more than $800 million.

Rite Aid had a market capitalization of $428.4 million as of Thursday's close.

The company will "as always, be responsive to credible proposals that will enhance stockholder value," it said. (Reporting by Manas Mishra and Amruta Khandekar in Bengaluru; Editing by Devika Syamnath and Krishna Chandra Eluri)