I'd talk to the cruising community in Langkawi -- most of them will have been there a while and would probably have a good handle on the issues with this trip.
Are you sure you want to go to Pattaya? It has a naughty reputation.
Naughty reputation is an understatement. If I had a better alternative, I'd go there, but Pattaya is the safest marina closest to home (Bangkok). Nearest alternative is Phuket...