HANOI--Leaders from Southeast Asia's five Mekong river countries were due to meet in Vietnam's capital from Thursday for two days of talks that aim to boost economic ties and trade across the developing region.

The prime ministers of the communist host nation Vietnam as well as Cambodia, Laos and Myanmar were set to meet on Thursday, then be joined by Thailand's new premier Somchai Wongsawat on Friday for a wider summit.

Except for middle-income country Thailand, the other four nations remain among the region's poorest and hope to build prosperity through closer regional transport and commercial links, both with each other and with China.

Vietnam, Cambodia and Laos were cold war battlegrounds until 1975, and conflict raged on in Cambodia until the 1990s. Military-ruled Myanmar, also known as Burma, remains diplomatically isolated and poor.

Thailand said Friday's meeting aimed to enhance ties in seven areas -- telecommunication links, tourism, trade and investment, agriculture, industry and energy, human resource development and public health development.

In the lead-up to the event, Cambodia's Hun Sen arrived Tuesday in Hanoi for talks with Vietnam's Prime Minister Nguyen Tan Dung and other leaders.

Both countries signed a number of agreements, including on visa exemptions, the transit of goods, and on a future railway connection.

Thailand's Somchai, who took office last month, on Monday visited his Lao counterpart Bouasone Bouphavanh in Vientiane.

When the Thai and Cambodian premiers come face to face at a dinner Thursday evening, the recent armed border dispute between the two countries over land around an ancient Khmer temple is likely to loom over the meeting.

Somchai said this week: "I may have a chance to see Prime Minister Hun Sen, but the talks will not be official because we have already agreed on how to work together. Everything is following the process and going fine."

Thursday's premiers' meeting is known as the fourth summit of the CLMV group, named after member-states Cambodia, Laos, Myanmar and Vietnam.

On Friday, the Thai premier will join his four counterparts for the third summit of another grouping, named after the region's major rivers, the Ayeyawady-Chao Phraya-Mekong Economic Cooperation Strategy, or ACMECS.

Senior officials of that group this week discussed developing the regional transport network, streamlining border and customs rules and promoting tourism through a "Five Nations, One Destination" initiative, said state media reports.