There are rainy seasons around Thailand, we always have a plan in case it rains, but we still recommend our clients not to plan the wedding in certain areas in rainy months:
Rainy seasons:
Samui, Phangan - November, December and August
Pattaya - September, October
Krabi, Phuket - July, August, September
Thailand has lots of beautiful destinations to offer. Take the weather into account when deciding where to have wedding.