Can I apply for a DTV visa in Ho Chi Minh City if I enter Vietnam from Da Nang Airport and my address is in Da Nang?

You apply for the DTV thru the thai consulate that serves the area where you stay in Vietnam (doesn't matter where you arrive it matters where you are in Vietnam when you apply for the visa)

The eVisa online system will give you a pop-up when you select you're in Vietnam and it will show the break down of who applies at what consulate

If you're in Da Nang you apply thru HCMC so you will be fine