There is no solid requirement to stop selling alcohol, apart from today (Sunday) because it is a Buddhist holiday.

People have been asked not to hold joyous events - hence some entertainment areas and venues have been closed. Their closure however is not by law, but because the owners have decided to. Entirely at the discretion of the establishment. (Again apart from today regarding alcohol). I don't think they will be closed for the full 30 days.

That being said, there is definitely a muted vibe in Bangkok, bands not playing, no loud music or celebrations. I was in ChiangMai yesterday also & there seemed to be less of an impact, although it is a more chilled out place to begin with.

Hotel lounges still serve alcohol today because they are private (as with the changes mentioned for these holidays at SGS)