- is the closest to Pattaya nice island. Most of travelers are Bangkok residents coming here for the weekends, as well as tourists from Pattaya. Beaches
are pretty good, but not so good as beaches of Phuket/Samui/Chang. Shore and seabed: sand, stones. 
The island has many hotels starting from 700 bahts per night. So it makes sense to stay here at least for one night. Find hotels in Ko Samet
How to get there 
Fly to Bangkok International Airport - Suvarnabhumi (BKK)
Taxi directly from the airport to Pattaya costs about 1500 bahts. Make sure to negotiate the price before the trip to avoid surprises. Journey will take from 1.5 to 3 hours depending on traffic.
There is also frequent bus service between the airport and Pattaya. It departure from Level 1 (Doors 7-8), costs about 150 baht per way and goes about 2 hours (or longer if traffic jams).
You need to get by bus or by taxi from Pattaya to Ban Phe
town, and next take a ferry to Ko Samet island. Find flights to Ko Samet
When to go 
The best time to visit Koh Samet island is a dry season from November to April. However, it's not too rainy here in summer.
Water temperature, C
Wind speed, meter/sec