Can I enter Thailand anytime within my e-visa's three-month validity despite my stated travel dates?

Visas dates are not personalised!

And you have a month's renewal once you're in Thailand

Travel to Thailand anytime within those 3 months, before the expiry date.

Spot on again tod

This question comes up a LOT

Don't confuse the validity of the visa <- (how long you have to ENTER thailand on that visa) with how long you'll get stamped in for once you arrive.

As long as you enter the country during the validity of the visa (the 90 days) you're fine no matter what you put on the application as far as your intended travel dates

if you applied for a single entry tourist visa it's valid for 90 days from the date they issued it meaning you have that long to enter thailand on it and when you do you'll get stamped in for the 60 day entry stamp you get on a tourist visa (even if you entered the last day the visa was valid for you'd still get stamped in for the number of days the visa allows on entry)

PRINT out that PDF they sent you in the approval email because it is your visa, hand it and your passport to the officer at passport control when you stamp in.