user3456: I imagine that it might be pronounced:

kye EE suh

kah EE suh

KAY suh

KYE suh.


Which is it? Or perhaps there is no established way and one shouldn't care too much.

user10439: How To Pronounce Caissa Please listen to all the options to get a sense on how to pronounce casissa. 

user9926: Short version:
I think that your best bet is probably option 2: "kah EE suh" (similar to the pronunciation of "naïve"). The phonemes match the spelling correctly (particularly the umlauted ï in "Caïssa" [ref. 1]), and it fits with the tonal stressing of multiple Thracian-related [ref. 2] languages.

Long version:
Historically, both Greek and and Turkish (largely Hittite and Assyrian influences, in Thracian times [ref.s 3 & 4]) would appear to have likely had the strongest early influences.
Satemization of the Thracian language [ref. 5] would indicate the initial “C” to typically be an “s” sound, though it seems that in the case of “Caïssa” it was more likely a “k” sound.
Given the remnants of the Thracian language available to us [ref. 6], there seem to be insufficient data to ensure “correct” pronunciation.  Thracian words seem [to me] to be equally likely to be most closely related to Latin, Greek, and several Balto-Slavic languages.
If Gottfried Schramm's derivation [ref. 7] is correct, then his Bessian-Albanian link would indicate that the “i” is indeed a “long e” (ï) sound [ref. 8].

References:

https://en.wikipedia.org/wiki/%C3%8F 
https://en.wikipedia.org/wiki/Ca%C3%AFssa 
https://en.wikipedia.org/wiki/Thracians 
https://en.wikipedia.org/wiki/Turkey#Prehistory_of_Anatolia_and_Eastern_Thrace 
https://en.wikipedia.org/wiki/Centum_and_satem_languages 
https://en.wikipedia.org/wiki/Thracian_language#Remnants_of_the_Thracian_language 
https://en.wikipedia.org/wiki/Thracian_language#cite_note-3 
https://en.wikipedia.org/wiki/Albanian_language#Vowels 


3456: <p>I imagine that it might be pronounced:</p>
<ol>
<li><p>kye EE suh</p>
</li>
<li><p>kah EE suh</p>
</li>
<li><p>KAY suh</p>
</li>
<li><p>KYE suh.</p>
</li>
</ol>
<p>Which is it? Or perhaps there is no established way and one shouldn't care too much.</p>
 10439: <p><a href="https://www.howtopronounce.com/caissa/" rel="nofollow">How To Pronounce Caissa</a> Please listen to all the options to get a sense on how to pronounce casissa. </p>
 9926: <p><b>Short version:</b></p>

<p>I think that your best bet is probably option 2: "kah EE suh" (similar to the pronunciation of "naïve"). The phonemes match the spelling correctly (particularly the umlauted ï in "Caïssa" [ref. 1]), and it fits with the tonal stressing of multiple Thracian-related [ref. 2] languages.</p>

<hr>

<p><b>Long version:</b></p>

<p>Historically, both Greek and and Turkish (largely Hittite and Assyrian influences, in Thracian times [ref.s 3 &amp; 4]) would appear to have likely had the strongest early influences.</p>

<p>Satemization of the Thracian language [ref. 5] would indicate the initial “C” to <i>typically</i> be an “s” sound, though it seems that in the case of “Caïssa” it was more likely a “k” sound.</p>

<p>Given the remnants of the Thracian language available to us [ref. 6], there seem to be insufficient data to ensure “correct” pronunciation.  Thracian words seem [to me] to be equally likely to be most closely related to Latin, Greek, and several Balto-Slavic languages.</p>

<p>If Gottfried Schramm's derivation [ref. 7] is correct, then his Bessian-Albanian link would indicate that the “i” is indeed a “long e” (ï) sound [ref. 8].</p>

<hr>

<p><b>References:</b></p>

<ol>
<li><a href="https://en.wikipedia.org/wiki/%C3%8F" rel="nofollow">https://en.wikipedia.org/wiki/%C3%8F</a> </li>
<li><a href="https://en.wikipedia.org/wiki/Ca%C3%AFssa" rel="nofollow">https://en.wikipedia.org/wiki/Ca%C3%AFssa</a> </li>
<li><a href="https://en.wikipedia.org/wiki/Thracians" rel="nofollow">https://en.wikipedia.org/wiki/Thracians</a> </li>
<li><a href="https://en.wikipedia.org/wiki/Turkey#Prehistory_of_Anatolia_and_Eastern_Thrace" rel="nofollow">https://en.wikipedia.org/wiki/Turkey#Prehistory_of_Anatolia_and_Eastern_Thrace</a> </li>
<li><a href="https://en.wikipedia.org/wiki/Centum_and_satem_languages" rel="nofollow">https://en.wikipedia.org/wiki/Centum_and_satem_languages</a> </li>
<li><a href="https://en.wikipedia.org/wiki/Thracian_language#Remnants_of_the_Thracian_language" rel="nofollow">https://en.wikipedia.org/wiki/Thracian_language#Remnants_of_the_Thracian_language</a> </li>
<li><a href="https://en.wikipedia.org/wiki/Thracian_language#cite_note-3" rel="nofollow">https://en.wikipedia.org/wiki/Thracian_language#cite_note-3</a> </li>
<li><a href="https://en.wikipedia.org/wiki/Albanian_language#Vowels" rel="nofollow">https://en.wikipedia.org/wiki/Albanian_language#Vowels</a> </li>
</ol>
