I have kept my current Thai number going for my last few visits, but I have a lot of work in the UK so might not be able to get back out for anything up to 8-10 months.

I would like to keep the Thai number. It is on 12call.

How much credit should I load it with to keep it active for that time?

Cheers

It is sometimes possible to buy airtime. Something like 3 baht for 30 days. Call One2Call to initiate the process.

You might already be there if you are a regular user. Dial *121# and the returned message will show you your balance AND how long it is good for.

Be aware that, in addition to your expiration date, nearly all plans here require specific activity: a top-up or making/receiving a phone call every 90 days in order to remain active. Options include leaving the SIM here with a trusted individual, or taking it with you, along with some top-up cards, with international roaming enabled, so you can make a call and/or top-up as required.

Example: from One-2-Call's Freedom SIM Terms and Conditions:

9. The company reserves the right to restrain the service in case of no calling, no picking up or no topping within 90 days.

In airport now so sorted it with AIS customer services (dial 1175 then 2 for English)

Changed all my credit to non-expired months at 30 Baht a month, so have until May 2012. If I don't make it back before then I will top myself LOL.

I can make a small top up every 90 days via my K-Bank account online to be on the safe side, but last time they did not stick to the 90 day rule as the terms posted.

Thanks for all your help.

Cheers

In airport now so sorted it with AIS customer services (dial 1175 then 2 for English)

Changed all my credit to non-expired months at 30 Baht a month, so have until May 2012. If I don't make it back before then I will top myself LOL.

I can make a small top up every 90 days via my K-Bank account online to be on the safe side, but last time they did not stick to the 90 day rule as the terms posted.

Thanks for all your help.

Cheers

I would just enable international roaming, then you can make 1 call every 90 days. Or just bring a few 50 baht top-up cards and top-up every 90 days from the U.K.

When you get close to the 90 day limit they will send SMSes reminding you to top-up or make/receive a call. At least that's how it has worked in the past. They usually don't recycle the number until 120 days.