Don't trust ME on this.
Contact your own visa agent to discover IF:
...you are in Vietnam from ANY country--on a category DN business visa--and you don't have a legitimate employer with a work permit--you will not be able to do any more 3-month extensions.
Or,
...you entered the country on a tourist visa on or after March 1st, 2020, your free automatic extension for this month (May, 2021) will be your final free automatic extension.
To quote my visa agent:
"It is said that automatic extension is ended this month and that all foreigners must find a way to leave Vietnam".
She also said this is brand new news, as just last week she was able to process 3 month extensions of business visas without a work permit.
She also said it's possible to get a paid 1-month extension of both types of visas, to allow for making plans to depart the county.
Don't shoot the messenger.
If you have proof that my agent is incorrect, by all means, please correct me with official data.