Prime Minister Prayut Chan-o-cha has reassured Japanese Prime Minister Shinzo Abe that the general election will be held in February next year.
He did not give a specific date, however.
In February of 2015, Gen Prayut also assured Prime Minister Abe, as well as Japanese businessmen, there would be elections in Thailand "towards year-end or in early 2016."
In both cases, in 2015 and on Monday, Mr Abe made no comment about Prime Minister Prayut's election pledge.
The two leaders met in Tokyo Monday to discuss enhanced cooperation between the nations prior to Tuesday's Mekong-Japan Summit, sponsored by the Tokyo government.
In a press briefing after their meeting in Tokyo, Mr Abe said Japan will work with Thailand to promote the Eastern Economic Corridor (EEC), a national project to develop a vast industrial area east of Bangkok, and train industrial personnel in the country. Gen Prayut, in return, thanked him and said that private investment from Japan will help to accelerate the growth of the EEC.
Thailand and Japan also confirmed they will promote free trade, with the Gen Prayut expressing his willingness to bolster the 11-member Trans-Pacific Partnership agreement following the withdrawal of the United States last year.
"Amid the spread of protectionism in the world, Japan agreed with Thailand, which leads the economic development in the Mekong region, on an early conclusion of the RCEP," Mr Abe also said, referring to another regional free trade pact involving 16 countries.
The 16 members -- Australia, China, India, Japan, New Zealand, and South Korea plus 10 members of the Association of Southeast Asian Nations (Asean) -- are aiming for a broad agreement by the end of the year.
Mr Abe also expressed Tokyo's willingness to help Bangkok assume the rotating chairmanship of Asean next year.
The two leaders also exchanged views on a variety of regional challenges, including North Korea, the South China Sea and the Rohingya crisis in Myanmar, Mr Abe added.
- Earlier report: PM promises election in 2019
