i realised that when i top up at more regular intervals (but smaller amounts), my expiry date gets extended for longer durations. but when i do it only as the card is about to expire and at larger amounts, i get 2 weeks to a month.

my guess is frequent recharge gives you longer validity and not the amount. in my 2 weeks that i did several small top ups, i managed to extend it by 6 months. but when i one big top up as the card is about to expire, i was given only 2 weeks.

Re the above few posts; I think you will find that the most annoying aspect of 'most' of the 1-2 Call plans is the very short validity that each recharge gives you and to do it from overseas, although fairly easy, becomes a hassle when you have to constantly remember validity dates.

1-2 Call plans have definitely reduced the validity periods.

Whilst in Thailand in May 2006, a friend set me up with a 1-2 Call plan called Kui Kum. It's feature was 3B for the first minute than 1B per minute after that.

Largish recharges of 500B used to extend the validity by 12 months. Now even though I'm on the same plan, 300B or 500B gives next to nothing in validity time.

I would have imagined that once you had locked into a plan, that the terms should remain the same. Apparently not!

Looking into DTAC. from what I've found out so-far, 12 month validity is available fairly easily, calls though 2B PM.

A small price to pay for peace! Although a hassle to change number after 3 years.

You can also buy top up credit online with paypal, and do the top up in your home country. Check on ebay or google "Thailand top up cards"