I'll agree with the Sukhumvit area, my first visit there being almost 30 years ago. Which predates some of the more flagrant entertainment areas.

Ideally you want a hotel about 1 or 2 blocks away from the main street.
Less noise but still convenient. Certainly much more action (of all types) between Soi4 and Soi 18 - This covers the main night market. OTOH don't ignore places like the Central department store chain when looking for purchases. Their main business is with upper middle class Thais and the prices are often quite good. And yes they have major souvenir sections.

I (and Mrs WF) find the 3* usually quite acceptable, since we only sleep and shower there. Normally use the Manhattan (Soi 15) The fanciest we have used is the Rembrandt (Soi 24 I think).

Enjoy your wandering

Fred