This page here: http://www.ais.co.th/one-2-call/en/package-addon-detail.aspx?type=1&id=19

has a nice summary of all AIS offers for pre-paid Internet.

I generally use the 1.5 Gb over 7 days @ 79B myself but I'm not a permanent resident.

There's a 8Gb over 30 days package @ 799B (Mao mao non-stop) that might suit you.

Prepaid is always more expensive than postpaid for monthly things.

8GB over 30 days for 799 baht is poor value, if he's getting 5GB over seven days for 99 baht.

Are any guys able to recommend PAYG card for IPad. It's really annoying at moment that I am unable to check balance or top up SIM card without removing card from IPad and inserting sim card in mobile phone. Currently using AIS prepaid card.

You don't need to do that with DTAC/Happy as their page will auto-login https://my.dtac.co.th/esv/en/login

True H too. Though I haven't checked it of late.

Only AIS still appears to use the one time password system. Strange, because it used to auto-login. Try it; https://eservice.ais.co.th/eServiceWeb/

See if it works for you.