Cambodia, Laos, Myanmar and China signed the MoU at the 19th GMS Ministerial Conference in Lao capital Vientiane that ended yesterday.
Thailand will sign the MoU for the Greater Mekong Railway Association (GMRA) in Bangkok, while Vietnam is in preparing government approval.
Arkhom Termpittayapaisith, secretary-general of the National Economic and Social Development Board, said Thailand was pleased to witness the signing of the agreement for closer cooperation.
A signing ceremony will be held soon for Thailand to join the GMRA.
The association will be housed with the Asian Development Bank (ADB) for the first two years of its operations and will aim to connect GMS countries to a rail network.
"The Thai government is also anticipating consideration of three remaining bills to give effect to cross-border transport agreements when the parliament resumes early in 2014, adding to two already approved, in order to maximise the benefits of economic corridors," Mr Arkhom said.
ADB vice-president Stephen Groff said yesterday's meeting also focused on a new generation of GMS initiatives.
Projects include urban development along transport corridors, building up regional power grids, establishing sustainable tourism projects, boosting environmental planning and management, and shoring up human resource capacity.
"These projects and initiatives are essential to help GMS countries, transform transport corridors into economic corridors and to ensure that future development is more sustainable and inclusive," Mr Groff said.