I'm a Thai national returning in a few days for about a fortnight. I'll definitely be in need of some reasonably reliable internet for my laptop, however I will be travelling around the country quite a bit and I don't really know what the best options or providers are. Apparently an AIS 3g dongle is worth considering but I'm not too sure about coverage. Any advice or recommendations you could make would be really helpful.

AIS is generally good for built-up areas but is terrible for country (especially in adverse weather). My wife had this problem and was advised to get True mifi. I think it costs about 1800 THB per month for 5GB and you can connect a number of devices. So far it has been excellent.