Sim For Blackberry Bis In Bangkok, Phuket, Krabi

[supermx]

Hello everybody! I'm going to Thailand for a month (Bangkok, Phuket, Krabi and islands nearby) and I'd like to use the BIS Blackberry service on my 9900 also there.

I need the possibility to check emails, browse the internet, BBM, etc (and in case also use the blackberry as a modem/tethering).

What do you suggest to do/get?

I don't know which is the best option between AIS, DTAC or TRUE...

My first thought was that the AIS should be the most reliable with better coverage, is it true? Do they work with EDGE or 3G?

I was thinking of getting the 12Call sim with Blackberry Unlimited for 799 Baht/30 days or is the DTAC BBmax better? (looks the same at 790 Baht/30 days)

By the way, do I just have to put my thai sim inside and will it work right away? I'm currently using "Wind" in Italy.

Thanks for your precious help!!!