Sorry if this question has been asked before, but I am not a regular visitor to this sub forum, and my experiences with the search function have usually been not so encouraging.

Is it possible to change from DTAC to for instance AIS whilst keeping the same number? And which network would in your opinion give the widest coverage?

Thanks in advance for replies.

Yes. The process is referred to as Mobile Number portability or MNP.

https://www.google.com/search?q=mnp+site%3Athaivisa.com&oq=mnp+site%3Athaivisa.com&aqs=chrome..69i57.6592j0&sourceid=chrome&ie=UTF-8

http://www.ais.co.th/mnp/

http://truemoveh.truecorp.co.th/mnp/how_mnp/entry/592

Yes. The process is referred to as Mobile Number portability or MNP.

https://www.google.com/search?q=mnp+site%3Athaivisa.com&oq=mnp+site%3Athaivisa.com&aqs=chrome..69i57.6592j0&sourceid=chrome&ie=UTF-8

http://www.ais.co.th/mnp/

http://truemoveh.truecorp.co.th/mnp/how_mnp/entry/592

I can confirm it works reasonably effectively. Wife & I moved from DTAC to TrueH 6 months back taking numbers with us. Can't remember how long the transfer took, it was in the order of a couple of days. You get a text msg when number transfer is complete

Personally, I would not switch from DTAC to AIS.

I had nothing but problems with all the other cell phone carriers.

I always recommend getting new evaluation SIMs, typically these cost ~ 50 baht, and one can subscribe to a daily (49 baht)/weekly (200 baht) plan for evaluation purposes. Once you've identified a provider which meets your requirements: coverage, call quality/completion, services & options, plan options, performance, customer service, web-based account management, etc., then port out/port in to the new service provider. I might even go with a pre-paid plan for a few months, to make sure you are satisfied, before potentially switching over to a post-paid/contract plan.

The MNP Clearinghouse is processing a lot of intra-provider (AIS/900 to AWN/AIS/2100, DTAC to TriNet, TrueMove to RealMove?) port outs/ins so not sure how the process is working for 'traditional' inter-provider ports?

The MNP fee was reduced a few months ago, from 99 baht to 29 baht.

Generally speaking CAT/TrueMove H with 850 MHz 3G - your phone would need to support this frequency - has the best/most coverage and the fewest customers, so they may be the best option. This assumes you need mobile data.

If you are just looking for voice services and/or your phone does not support 3G/850 MHz then AIS/One-2-Call or DTAC/Happy should be fine.

Easy, just put in a request with the company you are changing to. After filing in the paperwork, copy of passport or whatever, they will give you a SIM and in less than 2 weeks

your old sim will stop working and it will be time to switch to the new one. A trip to your old provider might be necessary depending on the type of account you have.

I recently switched from AIS (suxx big time) to DTAC (happy customer), and brought my number with me..

I recently switched from AIS (suxx big time) to DTAC (happy customer), and brought my number with me..

Exactly, did you drop them because you would put 500 or 1000 Baht on your phone at 7 eleven or family mart, only to find that 20 minutes later it's all gone?

I got ripped off approximately three times before I switched to DTAC. Since then, no problems.