i wouldn't pack too many warm clothes. depending how long visit is. daytimes will be nice, nights maybe 20's but rarely below. on a motorbike or in tuk tuk at night, the wind will chill you a bit.
last couple xmas get togethers, i wore a blended wool suit,

, same one,

, don't tell anyone. maybe good for one more wearing. anyway, one year comfortable, last year or before, too hot, actually stopped at hotel for quick change before next venue. one year, same time, abouts, friend came to visit, and temp dipped a bit at night and we were tuk tuking the bars, quite chilly, so i simply bought a 200 baht jacket from night market, as we started there. actually turned out to be a decent jacket, lasting few years and a few wearings. will use a lot this year, my motorbike jacket, ruin that with the smell of fumes first, till the zippers start failing.
so pack light, nothing here you can't buy if you need, and then just leave it here for next trip.
enjoy.
