There has been a topic on how to extend your expiration time on DTAC but thought an up to date topic may be useful. I pursued it as I needed to extend mine. Day Give-Away

I used this one which worked perfect. Dial - *113* + number of days *9#

Example *113*180*9# to get 180 days expiration extension.

That's a handy keypress code to get up to one year validity on DTAC Happy. There is also a whole list of keypress codes here.