You almost never need warm clothes in Thailand but this time of year in Pattaya some ladies opt to cover up during the cooler nights. Night temperatures have gone down to 18-20° C. If you are from a cold climate it may be mildly amusing to see the motorbike taxi drivers lighting fires to keep warm while others walk around in t-shirts and shorts as usual.
Some bars on Soi 6 are running free warm hug promotions and other attempts to make the most of the increase in clothing required. Not to fear though as revealing clothes and uniforms are still the norm in most bars around LK, walking Street and of course on soi6. You might choose an enclosed bar if the climate is not comfortable outside.