intrinsic was SEATO Doom from the begin
There founding member were in 1954 Australia, New Zealand, Pakistan, the Philippines, Thailand, France, Britain and the United States.
in 1955 began decolonize of France Indochina, with the new nation Laos, Vietnam, Cambodia.
also Britain decolonize Burma, Malaysia, Singapore. In 1963 Britain had only Hong Kong in asia
Those new and other regional countries like Indonesia were far more minded with domestic internal stability rather than concern of communism threat
They even refuse joining SEATO, now there members were not located in Southeast Asia!
Then came Vietnam War with USA attack North Vietnam what cloy even more the Southeast Asia Nation and SEATO became a Paper Tiger
on the other hand Ferdinand Marcos dictator of the Philippines consider SEATO as additional cash self-service.
Pakistan pull out after 1971 war with india, were SEATO gave none support to it member Pakistan
also pulle members like France and Britain the fincial support for SEATO
so in 1977 the USA formally dissolved SEATO.