The Dawei development on Myanmar's southern Andaman coast is a key part of the impoverished country's plans to transform its economy, giving neighbours such as Thailand an outlet to the Indian Ocean and markets to the West.
But the project -- led by Thai industrial giant Ital-Thai -- has faced resistance from local villagers and there have been signs of funding troubles.
The two countries signed a memorandum of understanding on the development of a special economic zone for Dawei, with Thailand agreeing to provide assistance in areas including security, infrastructure and logistics.
Thai Prime Minister Yingluck Shinawatra told reporters after talks with visiting President Thein Sein on a twice-postponed trip to Bangkok that the two nations would set up ministerial-level contacts to address related issues.
"In our talks, I reaffirmed the commitment of the Thai government to push forward with this cooperation with Myanmar in regard to the development of the Dawei deep sea port to have concrete progress," Yingluck said.
The Dawei project would include a 250 square kilometre (100 square mile) industrial area with a steel mill, petrochemical plant and oil refinery. The Thai developer insists all is going to plan.
It is among a number of ambitious foreign-funded projects which started before the long-ruling junta handed over power last year to a new quasi-civilian government whose ranks are filled with former generals.
But doubts about the port development grew after Myanmar's government earlier this year blocked a 4,000-megawatt coal-fired plant that was to be built at Dawei.
On Sunday Thein Sein inspected the Laem Chabang deep-sea port on Thailand's Gulf Coast, which is to be connected by road to Dawei, shortening the current sea route around the Malay Peninsula.
The two leaders also agreed to open three new border crossings between the two countries -- in Chiang Mai, Mae Hong Son and Kanchanaburi -- in addition to three existing official checkpoints.
Thein Sein delayed a visit to Thailand in May that clashed with opposition leader Aung San Suu Kyi's appearance at the World Economic Forum on East Asia in Bangkok, in her first overseas excursion for over two decades.
The Myanmar leader again postponed the trip in early June.