Greetings, the following page http://thai-language.com/id/590260 has three definitions of the word 'unexpected':

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คิดไม่ถึง

นึกไม่ถึง

Could someone please add clarity here by showing how these words work and what the difference between them is.

Many thanks.

คาดไม่ถึง

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Well, you've got it right. They all mean "unexpected". You can use them interchangeably.

คาดไม่ถึงเลยว่าน้ำจะท่วมหนักขนาดนี้

คิดไม่ถึงเลยว่าน้ำจะท่วมหนักขนาดนี้

นึกไม่ถึงเลยว่าน้ำจะท่วมหนักขนาดนี้

The three sentences above have the same meaning.

Okay, I was assuming that they either colocate differently or there are subtle shades of meaning that I cannot find. If neither cases are true and the terms are interchangeable then that's great.

Thanks.