From that article:
Vietnam is currently connected with seven undersea cables: SMW3, AAG, IA, APG, AAE-1, SJC2 and ADC. Besides the recent breakage of the IA, problems with the AAE, AAG and APG cables that have been present since 2022 and early 2023 have yet to be fully resolved.
The SJC2 and the ADC are yet to be officially operational, while the SMW3 cable is outdated and about to be decommissioned.
The fact that Vietnam currently only has one fully functional undersea cable has caused internet speeds between Vietnam and the rest of the world to slow to a crawl.