Next trip I intend to bring my now unlocked S3 with me

However I have an existing normal sized Thai Sim on True - Pay as You Go

Can I keep the same number and upgrade to a one month option that includes a data package?

Furthermore which is the best one month data deal (with minutes and texts also)?

And how do I overcome the Sim size issue - at the moment I have the normal sized one?

I need to keep the same number as I have cards printed with that number on it

Can this all be done at the True Stand at the airport or is Tuk Com a better option - or is there a True Shop in Pattaya?

Thanks in anticipation...

Do you have TrueMove, or TrueMove H?

How much data do you require? Voice? Texts?

You should be able to exchange your mini-SIM for a micro-SIM at any True shop, including the airport. You will keep your same number.

TrueMove H have a dizzying array of plans, both bundles and a la carte, where you build your own.

http://truemoveh.truecorp.co.th/3g/packages/ismart/entry/594

Net-net, you can pretty much get whatever you require.

Maybe just have a read through the TrueMove H web-site, then follow-up with details re: your requirements, or questions.

Do you have TrueMove, or TrueMove H?

How much data do you require? Voice? Texts?

You should be able to exchange your mini-SIM for a micro-SIM at any True shop, including the airport. You will keep your same number.

TrueMove H have a dizzying array of plans, both bundles and a la carte, where you build your own.

http://truemoveh.truecorp.co.th/3g/packages/ismart/entry/594

Net-net, you can pretty much get whatever you require.

Maybe just have a read through the TrueMove H web-site, then follow-up with details re: your requirements, or questions.

Will look through thanks for the link

I am sure I just have TrueMove - I will check on my Sim and KBank link that I pay it with

Assuming you want 3G you'll have to switch to TrueMove H.

Can you share any history re: this SIM/account? When was the last time you used it?

FWIW, you can port your number out to any operator.

More details can yield focused recommendations.

The Sim is fully active it has an expiry date of October 2014 and was used in the early part of November 2013

My main question is can I add data to the Sim I currently own and keep my number with True?

Adding data is an easy part.

Assuming you're on TrueH and have money on your account, just punch in the code right from the dial pad and you get internet!

There are some plans that automatically renew each month (not on my screenshot but probably in the link provided by lomatopo).

My main question is can I add data to the Sim I currently own

Based on what little detail you've provided I am guessing that you have a TrueMove SIM.

TrueMove currently only offers low-speed GSM data (AKA: 2G: GPRS/EDGE). So yes, you could layer a mobile data plan onto your existing TrueMove SIM, after you exchange it for a micro-SIM.

TrueMove's GSM 1800 concession was due to expire on 15 Sep. 2013, but was given a 1 year extension.

I am assuming that you want high speed, 3G, mobile data? If so, you'll have to change from TrueMove to TrueMove H, retaining your number/account. Simultaneously you will exchange your old Mini-SIM for a new micro-SIM, TrueMove H will link you existing number to your new Micro-SIM. Then maybe add value, now, finally, you can subscribe to a bundled voice/text/data plan, or subscribe to a la carte voice, text and data plans.

You may have to do all of this True Shop.

Note that your validity/expiration may default to a rolling 60 day maximum; so no more 1 year cumulative expirations.

My main question is can I add data to the Sim I currently own

Based on what little detail you've provided I am guessing that you have a TrueMove SIM.

TrueMove currently only offers low-speed GSM data (AKA: 2G: GPRS/EDGE). So yes, you could layer a mobile data plan onto your existing TrueMove SIM, after you exchange it for a micro-SIM.

TrueMove's GSM 1800 concession was due to expire on 15 Sep. 2013, but was given a 1 year extension.

I am assuming that you want high speed, 3G, mobile data? If so, you'll have to change from TrueMove to TrueMove H, retaining your number/account. Simultaneously you will exchange your old Mini-SIM for a new micro-SIM, TrueMove H will link you existing number to your new Micro-SIM. Then maybe add value, now, finally, you can subscribe to a bundled voice/text/data plan, or subscribe to a la carte voice, text and data plans.

You may have to do all of this True Shop.

Note that your validity/expiration may default to a rolling 60 day maximum; so no more 1 year cumulative expirations.

That is perfect

So basically I can do all of this in the Airport on arrival - good news

Thanks guys!!