Association of Southeast Asian Nations in orthographic projection. Credit: Addicted04
“Units from the countries of ASEAN began their first ever joint military drills in Indonesia’s South Natuna Sea amid rising geopolitical tensions between major powers and protests against China’s activities in the South China Sea…The five-day non-combat operation is aimed at developing military skills, including maritime security and patrols, and the distribution of humanitarian assistance and disaster relief, the Indonesian military said in a statement.”
This is a step toward establishment of recognized norms and cooperative law enforcement by ASEAN members in the South China Sea.
Significantly Indonesia is taking a leadership role. Indonesia seems to be the most aggressive nation in ASEAN with regard to protecting their EEZ assets.
Chuck Hill's CG Blog 
Indonesia’s ASEAN presidency prioritizes unified defense approach.
https://ipdefenseforum.com/2023/09/indonesias-asean-presidency-prioritizes-unified-defense-approach/
Another report on the exercise.
Found this interesting,
“Furthermore, interoperability among ASEAN military forces for humanitarian evacuation missions will be critical in any Taiwan contingency. More than 730,000 ASEAN nationals are working in Taiwan, and evacuating them to safety will be paramount in any future military conflict across the Taiwan Strait.
“No single ASEAN member has sufficient air and sea-lift capabilities to evacuate their nationals from Taiwan. A joint ASEAN humanitarian mission may be necessary. Thus, ASEX 2023 could be the foundation to prepare ASEAN for such joint missions.”
https://www.realcleardefense.com/articles/2023/09/26/aseans_first_joint_military_exercise_981896.html