What SIM card should I buy for 180 days in Thailand: TrueMove, AIS, or Dtac?

I've used True and never had a problem anywhere. Here's a 4Mbs unlimited, never throttled, for 180 days for 2100 baht. It's only 4 Mbps streaming so web pages etc load at full speed. It's in Thai but you can use Google translate on the image.

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I've used True, Dtac and AIS. True now has good coverage in any built up area, even traveling in rural areas doesn't seem to be a problem for me now. I have noticed the speed drop occasionally in somee of the extremely remote corners though. True have a very extensive wi-fi service that's available free for subscribers if their phone services, shopping malls and 7-11s usually offer fast and reliable connections to it.

DTAC offer a very fast and reliable service in the built up areas but can be lacking occasionally in rural areas, I'm not sure about their free wi-fi availability so I can't say if it's as comprehensive as True. The big downside to DTAC for me was their constant barrage of unsolicited messages, I was under a constant barrage of spam messages from 3rd parties that DTAC refused to block.

AIS offers fantastic reliability and speed in most areas both urban and remote. They don't use the same frequencies for all their services so you need to check that your own phone is compatible if your bringing it with you.

These 2 links may help

I'd buy a sim on Lazada. I bought an unlimited internet sim with 30 min of calls a month for 1100 baht in April.

Price has gone up a bit, but still reasonable for a year.

Check this store - ranges from about 1300-1500 baht for similar now.

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Perhaps the best value are the DTAC and True sims being sold, especially through Lazada, for around ฿1000, with free phone calls and free internet @4bps for one year.

Seemingly, AIS, too, but a little dearer..

When you get here go into a mall, go to an AIS. Cheap as, 200-300 baht a month for unlimited data

Never had a problem with AIS in Isaan. 6 months unlimited internet at 6mbs 1800 baht. I use about 70GB per month and there has been no slow down or drop out. Phone coverage good too.

Ais outside of cities .. no doubt !

TrueMove best coverage nationwide. AIS fastest speeds where available.

I have True Move unlimited everything, 10mbps 300bht/mth. Been great for Hotspotting, top-up at 7-11 or True Move stores.

Where are you going in Thailand? AIS is better around Phuket if you go scuba or island hopping. True works okay but not in remote areas. True have eSIM now if you have Iphone that is good since you can run your domestic SIM same time. Not sure if others also offer.

I have True for 319B. Unlimited yes but the download speed goes down so much after a few days of heavy usage that I can barely download photos and forget about playing videos. I read there is never any true unlimited

AIS is going to have the best coverage outside the city and fastest speed inside.

I think dtac is a great value option for city life.

I have true because it was bundled with fiber.

I use TrueMove. It's cheap. I recommend arriving here, and going into their shops and see what plan is the best for you. They have shops at all the malls and Robinsons

I use Dtac. 320 baht total a month. Unlimited data. My girlfriend says their customer service and promotions are better.

Either one is good. But directly from a true or AIS shop. Insist on unlimited internet if you are staying.

All pretty much the same. Whatever you do, don't buy a simcard at the airport, wait until you get in town and go to a shop. Airports only sell tourist sims.

I use Dtac, I find the customer service better than AIS and True, reception wise it's all pretty much the same though. I pay 200 baht a month, unlimited data 4mb/s. Can go up from there.