Can I apply for a soft power dtv visa in Hanoi with recent finances and reuse documents?

There is no seasoning requirement in Vietnam so yes you can be successful with your funds, The same SP docs can be reused for a 2nd application.,

Finances: Recently certain posts have reported Hanoi approving DTVs with 500,000 THB available for as less as 10 days. While what's recommended is to have seasoned funds months based on requirements of embassy to show financial stability.

Hanoi: Usually has good reviews provided you are eligible and fill up the form well.

Date of application: Recommended date of applying should be < 3 months from the intended date of travel.

Date of soft power activity: Has to be post the intended date of travel. Many schools are willing to revise the letter in case of a rejection or cancellation but this needs to be discussed beforehand.

I hope this helps you!