Does the validity of my e-visa allow me to enter Thailand anytime within three months?

As Denzel said "explain it to me as though I'm a 2 year old"

Not another one 😂

You will probably be given the standard 60 days with the option of requesting a 30 day extension. You are free to return home earlier with no penalty (grin). But I DO admit that those wordings can be CONFUSING! (smile)

The three months 90 days is the validity, you must enter Thailand during those 90 days, Unless it's a Non O visa. Then it's different

Yes, you can travel any time within those 3 months. The validity on the e-visa ("Valid from" to "Valid until") is only the window in which you have to enter Thailand. It isn't tied to the dates you put in your application. The Thai foreign ministry says visa validity and period of stay are two different things, and the Thai embassy in Bahrain's FAQ covers this exact case: a validity that doesn't match your travel dates doesn't need fixing.

Your permitted stay starts the day you arrive, and the immigration officer sets it on your arrival stamp based on your visa type, for example up to 60 days on a tourist visa. So enter before the "Valid until" date, then check the stamp and leave by the date on it. Overstaying is fined 500 baht a day, per the Thai embassy in London.

The visa is valid from date of issue for 90 days, for you to enter Thailand. It then gives you up to 60 days stay.