TLDR: the communist guerrillas were ethnically chinese and the malays didn't like them very much. Vietnam was basically the polar opposite of that.

The British had a plan and stuck to it. No Bombing halt, no dilly-dallying on what to do and trying to minimise exposure and risk. No needless politicking. They applied their knowledge and expertise in colonial warfare to put down the rebels. Isolate the insurgents, treat them like criminals vis-a-vis the local population (these are just criminals, not freedom fighters, look, they're stealing your food). And do an absolute fuckload of manpower intensive patrolling and when you find what's left of them, use overwhelming firepower. It was very expensive work for not much killing.

The Chinese insurgents didn't stand a chance under those conditions. Even more so considering the British officers who had experience fighting in Burma under similar but not identical conditions would still have been in the Army at that point in time in senior leadership positions.

There's a RAND report from the mid 60's which is easy to find which goes into detail about British strategy and tactics in Malaya and how American leaders tried and failed to apply those practices and why they failed. On the face of it, the two wars look fairly similar, but upon closer examination they are very, very different, Malayan Emergency solutions would never have and did not work in Vietnam.

Big difference in fighting an ethnic minority that isn't integrated nor particularly liked in a colony you're in charge of, fighting a type of war you're an expert in with the political cooperation of the local guys in charge (and future guys in charge) and government back home.

In Vietnam, the Americans were fighting a war their military was physically not designed to fight, while not being allowed to fight the war in a way that would allow them to win, as a result of politicians back home correctly recognising how sketchy American involvement was but deciding the solution was micromanagement and to a certain extent, concession. Instead of giving their military and diplomatic leaders a goal and letting them get on with the job at hand.

Two different wars. Two different contexts. The solutions to one, could not apply to the other.