South Korea and Vietnam have signed a deal to cooperate on intelligence issues and set up mutual liaison offices in each others' countries. The agreement is not all that amazing, but it does reflect South Korea's increasing use of Southeast Asian nations for assistance in dealing with the North.
In 2002, Seoul announced plans to upgrade Vietnamese military equipment, a move designed not only to benefit South Korea's defense industry, but also to enlist Hanoi's assistance in restarting stalled inter-Korean talks. A 2003 meeting between the South Korean and Vietnamese Prime Ministers led to increased business cooperation (and there was a brief jump in Vietnam settings for South Korean movies and TV dramas). And in 2005 the two nations signed a bilateral trade agreement.
Pyongyang and Hanoi have relatively close historic relations due to similar past ideologies, of course, and North Korean pilots flew on the side of the North Vietnamese during the Vietnam War. But Vietnam also saw troubles with the North in 2004, when it ultimately allowed some 460 defectors passage to South Korea. Pyongyang reportedly withdrew its ambassador to Hanoi at that time. But relations between the two have recovered somewhat since then.
Now Seoul is enhancing intelligence cooperation with Hanoi, and continues to increase economic contact, particularly in the energy sector, with South Korean firms drilling offshore Vietnam. But Seoul is not only working through Hanoi. When relations between Pyongyang and Hanoi soured, Seoul turned to Indonesia, which is currently working to facilitate military dialogue between the two Koreas.
As Seoul looks for more control over its relations with the North, and tries to pull out of the U.S. shadow, it is enlisting nations that have little reason to try to overshadow Seoul or usurp its position. South Korea will still work with the United States, China and even Russia and Japan, but given the vested interests of those nations, the benefits of Southeast Asian facilitators is obvious.