Prime Minister Yingluck Shinawatra is scheduled to visit Naypyidaw, Maynmar\'s administrative capital, to attend the 4th Greater Mekong Subregion (GMS) meeting on December 19-20, Foreign Ministry spokesman Thani Thongpakdi said on Wednesday. The spokesman said leaders of the six GMS member countries -- China, Cambodia, Laos, Myanmar, Thailand and Vietnam -- will attend the meeting. The prime minister will be accompanied by Foreign Minister Surapong Tovichakchaikul and Energy Minister Pichai Naripthapan who would also hold sideline meetings with their Myanmar\'s counterparts on the issue of energy cooperation, Thani added. Established in 1992, with the assistance of the Asian Development Bank, the six countries entered into a program of sub- regional economic cooperation, designed to enhance economic relations among the countries. The program has contributed to the development of infrastructure to enable the development and sharing of the resource base, and promote the freer flow of goods and people in the sub-region.