A list of the largest islands in Thailand ranked by size.

What are the largest islands in Thailand? This is a harder question to answer than I thought. Usually Wikipedia would have a list, but the Wiki list of islands of Thailand doesn’t show sizes. There are other lists online, but there are discrepancies between lists.

This article attempts to rank the sizes, and in the footnotes you will see why this turned out to be a difficult task.

Largest islands in Thailand

Here are the largest islands in Thailand.

Largest islands in Thailand map

This map show the largest islands in Thailand by rank. I will keep updating when the data improves.

[Map of largest islands in Thailand.]

I have another Thailand islands guide that lists every island where you can stay.

Notes on island ranking

There isn’t an official list of the largest islands of Thailand, so the data varies from website to website. After compiling this list I have found errors, which other sites then copy that error.

I started making this list as an experiment to use ChatGPT as a research tool. I thought that if I could use AI to pump out accurately curate dozens of listicle articles per day then I would be on my way to becoming the most highly trafficked travel blog in the world. In the end, what I thought would be a quick copy-and-paste job has ended up costing me more time.

These notes list where I have got the size from, and any other conflicting notes.

Phuket

Phuket is undisputedly locked in as the largest island in Thailand. Every list mentions Phuket as 543 km², but does that mean Koh Phuket or the entire province?

The Wiki page for Phuket province says that Phuket province has an area of 576 km², but on the same page it says that it has an area of 543 km². This inconsistency sets the tone for the rest of this list.

[3 districts of Phuket province, made up one one giant island and smaller outlying islands.]

Ko Samui

Wikipedia and Google report Ko Samui as 228.7 km².

Koh Chang

Some sites have been listing Koh Chang as the second largest island. Ko Samui is the second largest island, while Koh Chang is the third. A website dedicated to Koh Chang posted an article about how big Koh Chang is. This site manually measured the island with an online mapping tool. The fact that a travel website had to do this highlights that there isn’t an official size from a government institution.

I had seen this article before, so I knew that there were lists mixing up the size of Koh Chang. Thankfully I knew this, because when I asked ChatGPT to list the 50 largest islands in Thailand I got this result:

ChatGPT gave me a jumbled list of islands. There were less than 50, some islands were listed twice, and the list wasn’t in order. I was planning to do a population list but that was going to make this even more complicated.

I immediately knew that Koh Chang was wrong, so I asked again:

This time I got a closer number, but still not the right number.

I found that Wikitravel was saying that Ko Chang has an area of approximately 429 square kilometres, which appears to be the source of the incorrect size. I have now edited the size on Wikitravel.

Ko Tarutao

Ko Tarutao is the fourth largest island in Thailand, though I can’t find a reliable source for the size. When I search “Ko Tarutao size”, Google shows this information box saying 152 km².

In the right-hand knowledge box, Google cites information pulled from Wikipedia. There is no size information on Wiki though, so Google appear to be using other sources.

Ko Pha Ngan

Search for “Ko Pha Ngan size” and you are presented with this confusing result:

Most sites favour Ko Pha Ngan as 125 km², but the Tourism Authority of Thailand says it is 168 km².

¯\_(ツ)_/¯

Koh Kood

Google says that Koh Kood (Ko Kut) is 111.9 km², but once again it can’t provide a source.

The TAT doesn’t offer an island size, but drops this double clanger on its Ko Kut page:

“It is ranked as the 4th biggest island in Thailand after Ko Phuket, Ko Chang, and Ko Samui.”

As you can see, the TAT is getting the 2nd and 3rd islands confused, and it has ranked Koh Kood incorrectly.

105 square kilometres appears to be a the most quoted, so I will go with Travelfish on this one.

Koh Yao Yai

Finding the size of Ko Yao Yai is another difficult task. Ko Yao Yai is the largest island in the Ko Yao Archipelago. The smaller island (Ko Yao Noi) shows up in search sesults when looking for Ko Yao Yai. When I Google “Ko Yao Yai size” I get 87.24 km².

When I search for “Koh Yao Yai size “87.24” km²”, there is no site that quotes that size.

Google have just pulled a “trust me, bro” on this one. Ironically, now that I am posting this information, Google will probably use Nomadic Notes as a citation source for the size of Koh Yao Yai.

The Ko Yao Yai Wikipedia only mentions that the area of the Ko Yao Archipelago is 147 km².

This site says that Koh Yao Yai is 92sq km, so I am using that.

Ko Phra Thong

Google says that Ko Phra Thong is 92 km², while Wikipedia says it is 88 km². I have left it as 88, but it bothers me that Koh Yao Yai and Ko Phra Thong could be in the wrong order.

Ko Lanta Yai

Ko Lanta Yai is the largest island of Ko Lanta, and the Ko Lanta district Wiki page has a very specific number of 80.82 km². Most sites are round up the number to 81 km².

Ko Lanta Noi

The Ko Lanta district Wiki page lists Ko Lanta Noi as 75 km², so I have gone with that.

Koh Yao Noi

I’m using the same site that measured Koh Yao Yai. This site says Koh Yao Noi is 45 km².

Ko Libong

Google and Wikipedia agree on 35 km² for Ko Libong. ChatGPT quoted 40.5, but I can’t find anywhere that quotes that size.

Unranked and unverified island sizes

Beyond the top 12 islands, I am not confident in listing the rest of the islands in size order. I went through the rest of the CHatGPT list, and over half of the sizes didn’t correlate with what is being quoted online.

Ko Phayam is quoted by Google as 34.7. Wiki has a page for Mu Ko Phayam which quotes Ko Phayam as 17.50. ChatGPT quoted 35.8.

Ko Klang is listed as 26 on Wiki and 16.3 on ChatGPT.

Ko Tao is listed as 21 on Wiki and 21.2 on ChatGPT.

Ko Ra is quoted by Google as 19.5 with no supporting link. ChatGPT came up with 16.7.

Ko Phaluai is listed as 19.1 on Wiki and 16 on ChatGPT.

Ko Sichang is only listed as a district on Wiki, and it counts the size of 17.3 including the little islands around it.

Ko Samet is another confusing result. Here is the Google answer:

Google says an extremely specific 5.127 km², while the Wiki link it refers to says it is 13.1 square kilometres. It could be that the California-based Google is referring to square miles, even though the rest of the adult world uses square kilometres as a unit of measurement. I could be doubly wrong about this, but I’m going with 13.1 in this case.

Ko Mak is quoted by Google as 12.4 with no supporting link. The TAT of South Africa says it is 16, while ChatGPT says 16.35.

Ko Phi Phi Don is listed as 9.73 on Wiki. Other listings show the size for all of the Phi Phi Islands.

Disputed island sizes

Some island sizes have no source or wildly conflicting information. Consider this my too hard basket. I have found that the best way to get information on the internet is to be wrong about something, so here is a bunch of probably wrong information.

Ko Klang is listed at 28 km², while the Ko Lanta district page says that Ko Klang is 165 km².

Ko Surin Nuea is the largest island of the Surin Islands. I couldn’t find any island sizes for this group, and any sizes I found appear to refer to the area of the marine park (that includes islands and water). ChatGPT hallucinated the size of 32.8 for Ko Surin.

Ko Jum is listed as 12 on ChatGPT but I couldn’t find a reference for any size.

Ko Hong is listed as 10.1 on ChatGPT but I couldn’t find a reference for any size.

How to improve the list of island sizes of Thailand

A good start to improve this list would be that every website that is dedicated to an island should make a measurement like iamKohChang.com did.

I tried making a calculation by using CalcMaps. My ChatGPT list was showing Koh Lipe as 2.57 km² but there is no mention of this online. I calculated the size to be 2.13 km².

[Koh Lipe size by CalcMaps.]

Measuring with an online tool doesn’t account for the coastline paradox. This is not going to produce an exact figure, but it’s a good start.

The most logical place to seek the accurate size would be with the Royal Thai Survey Department. I tried to visit this site but it was not working (and I am in Thailand). If you have never dealt with a Thai government website, they are often down, point to broken links within their website, have spinning gifs (if the image isn’t broken), and have grainy maps that are 500 pixels wide.

A better source of information might be with a university. I see that Chiang Mai University had the first Geography Department in Thailand, so I will contact them for help. There might already be a list that no one has thought to upload. If not, they can claim the search engine ranking glory by providing the most concise list of the largest islands in Thailand.

– Cover photo is Nai Harn Beach, Ko Phuket.