Both the firms have signed shareholding agreements to establish two joint companies in which Ratchaburi will hold 60% stake and Chow Steel will own the remaining interest.
The initial investment phase will cover two projects with a combined capacity of 33MW that are expected to start commercial operations in 2016.
The companies will invest in 10.8MW Ueda solar farm project, located in Nagano prefecture, and 22.6MW Iwaki solar farm project in Fukushima prefecture.
Both the projects have 20-year power purchase agreements with major off-takers of the region.
Ratchaburi chief executive officer Pongdith Potchana said: "Partnering with CHOW Steel Group that has extensive experience and expertise in doing business in Japan will help increase our business opportunity and competitiveness.
"The common aim to expand renewal energy investment also helps drive our co-invested solar power projects in Japan toward success."
Chow Steel Group chief executive officer Anavin Jiratomsiri said the partnership is considered to be another significant step in expanding the renewable energy business to Japan where there are great opportunity and potential investment.
"According to the Japanese government’s intention to increase the solar power production capacity, Japan is regarded as attractive destination for renewable energy investment from most international investors. We believe that the synergy between the two parties will enhance our competitive advantages and accomplish ultimate goal as targeted."
