Is it just me, or is that a very hard query? Koh Lanta is pretty obscure. Croatia while not as obscure, won't have the tourist pages like say Italy, Greece, China, etc.
The chances of an actual web page having both of those words that is not spam seems pretty low to me.
You would have to do some type of word vector for "Koh Lanta" and then try to find a location in Croatia that matches the word vector.
LLMs might actually be better at this. Bing chat gives me the following in response to
"what is the koh lanta of croatia?":
"I assume you are asking for a place in Croatia that is similar to Koh Lanta, Thailand. Koh Lanta is an island in the Andaman Sea south of Krabi, Thailand, known for its low-key vibe, beautiful beaches, and amazing food 1. Unfortunately, I could not find any direct comparison between Koh Lanta and any place in Croatia. However, Croatia has many beautiful islands with stunning beaches and crystal-clear waters. Some of the most popular islands in Croatia are Hvar, Brac, Korcula, and Vis 2. Each of these islands has its own unique charm and atmosphere. If you could provide more information about what you are looking for, I could help you find a place in Croatia that suits your preferences. "