Japan's Mitsubishi UFJ, the country's largest lender, said Tuesday it planned to buy 75 percent of Thailand's Bank of Ayudhya for about $5.6 billion.
The deal, which is subject to regulatory approval, would be the biggest by a Japanese lender in Southeast Asia.
"With its potential for future growth and a track record of consistent economic growth, Thailand has become an economic centre of Greater Mekong," Mitsubishi said in a statement.
"Thailand and Japan enjoy a close relationship with numerous Japanese companies now operating in Thailand," it added.
"(Bank of Ayudhya) is one of the leading commercial banks in Thailand offering diversified financial services while holding wide range of client base and market knowledge."
Mitsubishi said it would offer shareholders, including US-based General Electric, a price of 39 Thai baht ($1.25)per share.