When you land at the airport, I recommend buying directly the dTac Happy Tourist SIM card for 299 Baht. You will get 100 Baht credit for phone calls and sms and 1gb of data at 42 Mbps for 7 days.
I’m using Google maps and when I arrived at the hostel in the night, the lady was not there for the checkin and I had to call with my swiss number and pay a high roaming just for a 1 minute conversation.
Wish I had the dTac sim card already… So if you need connectivity, go for it.
Important: to activate Internet follow these instructions (you must download the settings and install them in your phone, if asked, the code is 1800 as you may have seen in the messages)
When you land in Bangkok, just after the passport control you will be able to withdraw money with your VISA credit card (see my post about the DB credit card: I just got 20’000 Baht and no DKB fees. Only 150 Baht for the ATM).
Don’t lose time as I did, looking for an international bank to avoid the 150 Baht fee. I asked and a guy at the airport told me that there is no ATM without fees, at the airport. In the city you may find the AEON bank or other international banks, but not at the airport.
So, if you need money, just go to the first ATM you find and withdraw 15’000 Baht or 20’000 or entering your custom amount and that’s it.
Update: I kept all the reseeds for all the withdrawals (I took a picture with the phone) and at the end of the trip I sent an e-mail to DKB. DKB refunded me all the ATM fees. The DKB-Cash Visa credit card is just awesome!