MANILA (Reuters) - The Philippines' most valuable firm, SM Investments Corp, is planning to invest at least $300 million in an integrated casino and resort north of Manila, two sources with knowledge of the matter said on Wednesday.

Premium Leisure Corp, a subsidiary of SM's Belle Corp unit, has applied for a licence to build and operate a casino and resort in Clark, a former U.S. military air base turned into a leisure and business hub, in Pampanga province, the sources said.

"Aside from the casino, there will be a convention centre and a hotel," one of the sources told Reuters.

Premium Leisure, which delisted from the stock exchange earlier this month, is the landlord of the $1 billion-plus City of Dreams casino-resort, which is operated by Nasdaq-listed Melco Resorts & Entertainment Ltd, in Manila.Officials of SM, Belle, and Premium Leisure did not immediately respond to a request for comment.

SM, with a market value of $18.81 billion, has interests that range across shopping malls, banking, residential and office towers, retail, mining, and logistics.

(Reporting by Neil Jerome Morales; Editing by John Mair)