Well, I'm heading the first of October to Thailand, Samui and would like to thank the people giving information here, I've been reading a lot of posts.
About withdrawing money I've decided to resign myself for the moment to make wire transfers to my local bank account at Spain.
But anyway get a bank account in Thailand just in case I can use it with MB.
(It seems once you get outside of the country you could.)
Also try with a Visa Card from Thailand, but I'm afraid this won't work.
And use when you need to go out of the country for the Visa, to go somewhere that you can make transactions, like Singapore or Hong Kong.
About Internet, I'm thinking about using the WIFI net on the island. It's 1500 bahts a month, and if it works well it can be very handy. I'm not thinking about using a VPN so really don't need that much speed. (I've tried playing at Spain with a dial connection and it worked great.)
Regarding accommodation I've booked a hotel for the first days at http://www.sawadee.com
, and I'll be riding around the island looking for nice house to rent.
I have also heard Chiang Mai is a nice mountain spot with good ambient, and internet at the north of the country.
Hope, this help someone.