Meiji Yasuda Life Insurance Co., the nation's third-biggest life insurer, said it agreed to buy a 15 percent stake in closely held Thai Life Insurance PCL to meet rising demand in the Southeast Asian nation.

The deal is worth about ¥70 billion, one of two people briefed on the transaction said earlier, asking not to be identified as the process is private. Meiji Yasuda will appoint one director to the board of Thai Life, the Japanese insurer said in the statement posted on its website. The statement didn't give a value for the deal.

Insurers from London to Tokyo, attracted by Southeast Asia's emerging middle class, have spent over $6 billion acquiring assets in the region over the past two years, data compiled by Bloomberg show. Dai-ichi Life Insurance Co. agreed to buy 40 percent of PT Panin Financial Tbk's life insurance unit in Indonesia for 3.3 trillion rupiah ($330 million) in June.

The sale values Thai Life at a multiple of 5.9 times the value of its net assets at the end of March, more than double the average of 17 publicly traded Thai insurers, according to data compiled by Bloomberg. Bangkok Life Assurance PCL is valued at 3.49 times book value, the data show.

Tokyo-based Meiji Yasuda is building its overseas insurance business and seeking to expand in markets including Asia and South America, its website says.