AIS vs DTAC vs True: Thailand’s Three-Way Network Race Explained

AIS wins on raw coverage, especially outside Bangkok. True, which absorbed dtac, sits close behind in the cities and now shares a good chunk of AIS’s rural reach too. That’s because the two-year network merger between True and dtac formally finished in October 2025. Dtac, as an independent network, effectively stopped existing that same month. It lives on today only as a brand name riding on True’s infrastructure. If you take one thing from this guide, take that: you are not really choosing between three Thai networks in 2026. You are choosing between two.

Why the “three-way race” framing is outdated

Most comparison articles still describe AIS, dtac and True as three separate competitors. That was true in 2020. It stopped being accurate somewhere between 2023 and late 2025. Almost nothing written about Thai networks explains why the shift matters for a traveler holding a SIM card at a 7-Eleven counter.

True Corporation and dtac completed their corporate merger back in March 2023, under approval from Thailand’s regulator, the National Broadcasting and Telecommunications Commission (NBTC). For two and a half years afterward, the companies kept running semi-separate networks, patched together through roaming agreements between towers. That’s the version most existing guides describe.

That version ended on 13 October 2025, when True announced it had finished its “One Network” project, previously called Single Grid. According to Developing Telecoms, the project consolidated the tower assets and spectrum bands of both networks into one physical grid, run by more than 3,650 engineers across 17 million work-hours. Spectrum pooling means a phone that used to sit on the old dtac grid now draws on the same combined 700 MHz, 850 MHz, 1800 MHz, 2100 MHz, 2300 MHz and 2600 MHz bands as a True phone. There is no separate dtac network left to compare against. There’s True, and there’s the dtac brand sitting on top of it.

There’s a second, less-reported consequence of this consolidation, and it explains why tourist SIM choice narrowed over the past year. By August 2025, every remaining mobile virtual network operator in Thailand — smaller resellers like Penguin SIM, Fields Telecom and redONE — had shut down after losing wholesale access to the merged network. Thailand’s mobile market, which once had a handful of budget resellers alongside AIS, True and dtac, is now genuinely a two-operator market for practical purposes. That’s worth knowing if you’re wondering why some of the cheap third-party SIM brands you remember from a previous trip have quietly disappeared.

AIS: still the network with the widest safety margin

AIS remains Thailand’s largest operator by a clear margin, with roughly 45.7 million subscribers and around 44% of the national mobile market. Coverage is where AIS earns its reputation. Independent testing from Ookla named AIS Thailand’s “Best Mobile Network” and “Best 5G Network” for the second half of 2025, based on speed and consistency across the country, not just the capital.

In practice, that shows up most on the routes where travelers actually get caught out: ferry crossings between Koh Samui, Koh Phangan and Koh Tao, the mountain switchbacks on Route 1095 toward Pai, and the summit road up Doi Inthanon, Thailand’s highest point. On several of these routes, testers and locals report AIS holding a usable 3G or 4G signal well past the point where other networks drop to nothing. In Bangkok and Chiang Mai, AIS’s own city speed tests have shown download speeds in the 105–177 Mbps range on 5G, with 4G medians closer to 65 Mbps.

If your trip includes islands beyond the main resort strip, a rural home-stay, or a self-drive loop through the north, AIS is the lower-risk pick. You pay slightly more for a tourist SIM, and you get a wider margin of “it just works” everywhere your itinerary takes you.

True (with dtac folded in): strong in cities, catching up everywhere else

True Corp is now Thailand’s second-largest operator, formed from the combined True and dtac subscriber base of more than 50 million connections on a pro forma basis at the time of merger. Since the network integration finished, coverage gaps that used to separate “True” from “dtac” performance have narrowed noticeably, and True’s population-level 5G reach is now reported around 93%, not far behind AIS.

Where True tends to edge ahead is indoor signal in specific buildings, oddly enough. Expats living in high-rise condos around Bangkok’s Asok and Phrom Phong BTS stations have reported patchy AIS reception on upper floors that improved after switching to True — likely a case of which carrier has a rooftop small cell on that particular building, rather than a general rule. In dense city cores and resort towns like Phuket, both networks perform comparably well for maps, ride-hailing apps, video calls and social media.

The gap that remains is at the edges: deep rural roads, small outer islands, and mountain passes, where the old dtac towers were thinner on the ground than AIS’s and haven’t all been upgraded yet. True is closing that gap, but as of 2026 it hasn’t closed it completely.

So what actually happened to dtac?

This is one of the most-searched questions about Thai networks, and most articles answer it vaguely. Here’s the direct version.

• The dtac brand still exists commercially. It’s still sold at 7-Eleven, dtac-branded stores and airport kiosks, often as a cheaper-looking tourist SIM option.
• The dtac network, as a physically separate grid of towers and spectrum, no longer exists. It was folded into True’s infrastructure through the One Network project completed in October 2025.
• Buying a “dtac” SIM today means buying a plan priced under the dtac brand that runs on True’s combined network — not a distinct third option.
• The NBTC’s original merger conditions required True to keep True and dtac as separate brands for three years and cut prices by roughly 12% on average. Users have publicly disputed whether that price cut fully materialized.

For travelers, the practical upshot is simple: don’t treat “dtac” as a genuinely different coverage profile from “True.” Treat it as a pricing tier on the same underlying network.

Coverage and speed, side by side

Here’s how the two real networks compare on the metrics that matter for a trip, based on 2025–2026 data from Ookla, nPerf and provider disclosures.

Metric	AIS	True (incl. dtac)
Subscriber base	~45.7 million (~44% share)	~51–55 million combined pro forma
Nationwide 4G reach	~98% of population	Improving post-merger; official nationwide figure not disclosed to match AIS
Population 5G reach	~95%	~93%
Ookla 2H 2025 awards	Best Mobile Network, Best 5G Network	Not awarded top spot
Typical Bangkok/Chiang Mai speed	105–177 Mbps (5G), ~65 Mbps (4G median)	Competitive, generally trailing AIS on download; strong on upload in nPerf’s 2024 testing
Strongest for	Islands, ferries, mountain roads, rural touring	Bangkok, resort cities, indoor signal in select high-rises

Tourist SIM and eSIM pricing: what you’ll actually pay

Official tourist SIM packages from both networks typically range from 299 to 1,199 Thai baht, depending on validity and data allowance — roughly US$9 to $37. True’s own tourist plans run from about 449 to 1,199 baht. The cheapest physical option is usually a basic 7-Eleven SIM, often around 15GB for 8 days, though you’ll need to install the carrier’s app to activate the data package yourself, which trips up a fair number of first-time buyers at the counter.

Here’s the part that most SIM-versus-SIM comparisons skip entirely: if you’re buying an eSIM rather than a physical card, you don’t actually pick AIS or True yourself. Your eSIM provider has already chosen a host network through its own roaming agreement, and your data rides on whichever network that provider has partnered with. Most Thailand eSIMs, including budget global providers, route through AIS, True, or both, and the coverage you get depends entirely on that backend choice rather than the brand printed on the checkout page.

This is worth checking before you buy, not after you land. If your itinerary leans toward islands or rural routes, look specifically for a provider that discloses AIS as a host network. For a closer look at how different eSIM providers handle this in practice, I put together a full Thailand eSIM comparison after testing a handful of them across a Bangkok-to-islands trip.

A quick decision guide

• Bangkok-only trip, short stay: either network works fine. Pick on price.
• Islands, national parks, mountain roads, or a self-drive loop: choose AIS for the wider safety margin.
• Long-term stay in a Bangkok high-rise: test both if you can — indoor signal varies building by building.
• Tight budget, city-based trip: a dtac-branded tourist SIM from 7-Eleven is the cheapest reliable option.
• Buying an eSIM: confirm the host network before checkout, especially for island or rural itineraries.

Frequently asked questions

Does dtac still exist as its own network in 2026?

No. Dtac remains a brand name and a pricing tier, but the physical network it once ran on was fully absorbed into True’s infrastructure when the One Network integration finished in October 2025.

Is AIS or True better for Bangkok?

Both perform well in central Bangkok. AIS holds a slight speed edge in most independent testing, while True can outperform locally in specific high-rise buildings depending on where the nearest tower sits.

Which network do Thailand eSIMs use?

It depends on the provider. Most route through AIS, True, or a mix of both, based on their own wholesale roaming deals. Always check the provider’s disclosed host network before buying, particularly for island or rural travel.

Is True the same company as dtac now?

Yes. True Corp and dtac completed their corporate merger in March 2023 and finished merging their physical networks in October 2025. Dtac now operates as a brand under True, not as a separate carrier.

What’s the best network for Thai islands?

AIS generally offers the strongest and most consistent coverage across Thailand’s islands, including ferry crossings and less-developed coastlines, based on independent testing and on-the-ground reports through 2025 and 2026.