First time, 5 nights, no nightlife. Silom vs Ari vs somewhere quieter than Nana. I land late so I do not want a 45 minute Grab just to "be in the centre".

Ari if you want quiet and cafes. Silom if you want BTS and you land at Suvarnabhumi. Airport Rail Link to Phaya Thai then one hop. Nana is the one I would skip for sleep.