My flight arrives in Bangkok at 7.30 PM (evening). I would like to go straight to AranyaPrathet (or part of the way) rather than go into bangkok. Any advise how i want do this?  Any buses/van going from airport or a nearby city i can get to from airport at this late-ish hour

I could only think of a bus/van to Pattaya, then getting a van to Aranyaprathet. (There might be companies that did border runs before the pandemic, that may or may not offer such trips. Google is your friend.) I personally would play it safe and go to Morchit.

your flight arrives at 7.30pm,  I would suggest you ask at the airport if you can catch a mini van to Pattaya ... or if nothing available,  I would ask if anything goes to Mo Chit.    Either that or get a taxi.  

Get to Chachoengsao town from the airport.  It's in the right direction and you'll have an option of bus or train the next morning.

11 minutes ago, treetops said:

Get to Chachoengsao town from the airport.  It's in the right direction and you'll have an option of bus or train the next morning.

That's the direction to go.

Just that I found the last van from the transport terminal seems to go at 8 PM?