I've seen some posts about re-entry permits.

 

I have a ME non-O, expires September 2019, one use last year.

 

Do I just arrive at Suvarnabhumi for my next entry, or is there something else that I need to do beforehand?

 

Thanks.

You don’t need a re-entry permit.

 

As long as you enter before the visa expires you’ll be granted a new 90 day stay, You don’t need to do anything else.