I think the taxi to Ban Phe pier is 1,000 baht one way. An Ebike could pay for that real quick.

 

I can run 10 miles but as a cyclist I'm probably amateur level due to different muscles used. Is a trip of that length and terrain doable or considered an advanced route? Google puts the trip at 82 km long. So about 4 hours at 20.5 km/hr

Why not do some 2 hours trips locally and see how you feel, then bump it up to 3 hours then 4, carrying the same gear you would take as a trip to Koh Samet.

2 hours ago, bbko said:

Why not do some 2 hours trips locally and see how you feel, then bump it up to 3 hours then 4, carrying the same gear you would take as a trip to Koh Samet.

I may not get the bike if a 50 miler is too much. but i see what you mean, the most important feedback is my own body's

Easy-peasy fitness wise for you. No e-bike needed.
As suggested, build up to it to acclimate the muscle groups and your butt!
Tip: The latter may be your biggest hurdle. Don't be suckered into gel seat and get some decent cycling pants.

You don't need an e-bike.  You can do this on a regular road bike or gravel bike if you like.  Running 10 miles is much harder than cycling.  You just need some time in the saddle to get your legs and butt used to the cycling.  

As stated, should be easy, if you're in good health, and condition.  I've done 100 kms on a pedal bike, mostly level terrain, so on an ebike, it would be easy.  PAS & battery size and you may make on 1 charge.  

 

Hardest part will be buying an ebike, that has accurate specs ... ????  I converted a Schwinn to an ebike, and 1 battery I have for it, wasn't even close to it's spec, but inexpensive, and I did get what I paid for.   Use it a spare now, to a battery with lower specs, but lasts more than 2x longer ... ????  but also cost twice as much.

 

Happy riding.