With the introduction of smartphone, travellers now have an increasing need for prepaid SIM with 3G or data services. For Thai travellers, there are 3 main telcos to consider: AIS, True & DTAC
Of the 3, DTAC probably offer the best package of them all and the easiest to use also. Coverage with Bangkok is generally acceptable so far.
- For 299 baht, you get 1 week of data (with 1 GB cap after which speeds drop)
- Or you can select 49 baht/day usage for shorter journeys, top up can be done at most convenient stores
I used True and AIS before. True has really a difficult volume or hour based data usage per month/day. So if you get a monthly package, you cannot top up if you use up all the data until one month later. The closest you get to daily unlimit is the D1 package which gives you 2G for 24 hrs unlimited. But in terms of speed, I think true is the only provider with true 3G at the moment. Yes the other 3G rides on top of 2G spectrum and not a true 3G spectrum, so much for protests and Thai politics.
For AIS is easier, with volume based usage. You can top up once the volume is used up. But I had almost no connectivity when I was around Rama 3 at Narathiwas, which is still in town for me that last time I used it. So I ditch it, even though its the biggest Telco in Thailand. Please note that this was almost 1.5 years ago.
Also, an avid bird watcher friend mentioned that AIS signal remained available (with 2G) when trekking in the nature reserves whereas True and DTAC had no signals at all, not unexpected as AIS is the biggest in Thailand. So if you are heading out into the wilderness or outskirts, you should consider AIS.
Notable update 2013-05-08: 3G services has finally started to roll out in Thailand. In terms of connectivity, it might be different and better over time. I believe the data packages may change with the roll out of 3G services; let’s wait and see.
http://www.bangkokpost.com/news/local/348897/thailand-3g-era-officially-startsChoosing Prepaid SIM data package in Thailand