What are the entry requirements for the DTV visa after approval?

It’s true, after 3 months you will have to visit a dentist and get root canal treatment

I recommend @Thonglordental

Short answer is no, there’s no activation period and you can enter any time between the date the visa is issued and the day before it expires in 5 years.

The 3 month/90 day thing comes from people conflating embassies not wanting to process applications with an intended arrival date of more than 3 months out and single entry visas such as Non-Immigrant O, B and ED or a SETV which are valid for 90 days.

No but to apply for the DTV you need to show that you plan to enter Thailand within 3 months

No, the visa is valid for 5 years. Not 3 months.

You have 5 years to enter Thailand from date of issue.

No

That is not true. You can enter and leave as you please during the 5 year visa term.

That's with UAE 5 year visa where visa "activates" only when you enter within 60 days. DTV activates from the date of issue for a total of 5 years. No other rules.