Nippon's share was acquired from Premier Oil Plc, which recently withdrew from the project, and was made despite the potential risks of investing in the SEA country due to its unstable political climate.
The project, which first began in May 2000, currently produces 7.8 million cubic metres of gas from three offshore gas blocks - M-12, M-13 and M-14. The gas is exported to Thailand for use in the Thai power utility industry.
Nippon's stake in the venture now stands at 19%. The other partners are Myanmar Oil and Gas Enterprise, PTTEP International Ltd and Petronas.