That could be it, but I'm failing to see the significance of that as the US already has a defense treaty with the rest of AUKUS, Japan, the Philippines, South Korea, etc.
Forming that into a single organization now could be nothing more than theatrics and would be seen very negatively and warily in the region.
Not to mention bringing the European NATO in, who could not help much tangibly/militarily the US, but would decimate their image and perception in the region to the lowest possible level. If you follow the ASEAN, they are against forming regional blocks as much as possible.
Also, China is ASEAN's biggest trade partner, investor, infrastructure provider, and technology transfer source - with some exceptions like the Philippines who choose to confront China.
At this point, it is not a question of whether the ASEAN will join the US against China, but whether ASEAN will allow the US to attack China and further escalate the situation in the region without a response from them.
They are also certain to officially deny and close their air spaces and territorial waters to the US Navy in the case that the US goes to invade China or tries to disrupt regional shipping, might even employ asymmetrical warfare against them just like Houthis, but much more effective.
It is just that in this case it will be probably China who is going to direct this with intel and missiles/drones, instead of Iran in the case of Houthis.
Source:
With regards to closing of the Straits of Malacca by QUAD, AUKUS or any funny acronym alliances in times of conflict with China – ASEAN will not allow it as the Straits of Malacca is a major artery of world trade as 40% of world trade passes though it, and closing it will have severe impact on world economy and on ASEAN itself. If any acronym alliances were to use military force to close the Straits of Malacca, then it will become an enemy of ASEAN – ASEAN will then partner with China by opening its naval ports and airports to Chinese destroyers, drones and jet fighters to ensure Freedom of Navigation in the Straits of Malacca via joint patrol.
That's a very optimistic scenario. But I'm not that optimistic for ASEAN. After years of observing what communities of nations did during Covid, the Ukraine War, and the Israel-Gaza War. As an inhabitant of SEA myself, my gut feeling is that if and when the Straits of Malacca is blockaded, ASEAN will be very divided about what to do. Singapore, I suspect will be paralyzed by indecisiveness and confusion as it'll be split between the US and China. It'll be doing alot of diplomatic work and posturing, but it won't do anything too serious to anger either side. Malaysia and Brunei are just hopeless cowards. They will hide away from any fight. Myanmar will be too busy in its civil war and will stay out. The Philippines is the US's pet in SEA, so it'll support the US. So maybe, just maybe, Indonesia, Thailand, Vietnam, and the various Indo-China nations might actually have the guts to do something and join forces with China to re-open the SOM. Because these nations are the current growth engines for ASEAN, and have a future to fight for.