[simoncheng]

Originally Posted by Nonteerak2553

I've been using AIS, but switched to DTAC few months ago.
DTAC is cheap and good, every top up will increase your expiry date. And when first I purchased, the validity is 3 months, follow by per top will up another month.

Last time AIS have this plan, which is you can extend your validity for 20 bht, for every month, but that's was old plan. If one heavily uses the 3G, then I would strongly recommend DTAC. After the switch, I save lot of money for my 3G.

Another reason could be the shelf life of the prepaid SIM card itself. Most prepaid SIMs expire or lose their effectiveness after about 7-8 years usage. So there is no more extension period if the SIM card itself is expiring.