I would expect ศีรษะ would be written like this: ศรีษะ.

Does anyone know an explanation for the position of sara ii?

It appears to have a Sanskrit spelling with a Pali pronunciation. The Sanskrit root is ศีรษ, and the Pali is สีส. (The final ะ is implied.)

This type of hybrid origin is relatively common, due to the coexistence of words of both Pali and Sanskrit origins in Thai. As writing and literacy became more widespread, you begin to find these disconnects between how things are traditionally spoken and written. This is why words like ธรรม are pronounced [ทำ], too -- Sanskrit spelling, Pali pronunciation. The r is silent.

Also, it's not related to ศรี [สี], so it would be erroneous to spell it ศรีษะ.

Short version: it's just a silent ร.

It appears to have a Sanskrit spelling with a Pali pronunciation. The Sanskrit root is ศีรษ, and the Pali is สีส. (The final ะ is implied.)

This type of hybrid origin is relatively common, due to the coexistence of words of both Pali and Sanskrit origins in Thai. As writing and literacy became more widespread, you begin to find these disconnects between how things are traditionally spoken and written. This is why words like ธรรม are pronounced [ทำ], too -- Sanskrit spelling, Pali pronunciation. The r is silent.

Also, it's not related to ศรี [สี], so it would be erroneous to spell it ศรีษะ.

Short version: it's just a silent ร.

Very nice response!! A pity all questions regarding Thai language can not be explained so quickly and accurately

Edited May 18, 200917 yr by midasthailand

Thanks Rikker.

Thanks, Khun Rikker.

As a follow-up to Rikker's explanation, please see "รักภาษาไทย" by นววรรณ พันธุเมธา, page 485. She provides the same explanation that Khun Rikker does and it is a great reference book. It is a must for serious students of the language; and, all 614 pages for only 300 baht.

Short version: it's just a silent ร.

And it's ศีรษ, not *ศีร์ษ, because of the double-pricing rule that does not require a karan on silent word-internal ร of Sanskrit origin, e.g. สามารถ [M]sa[F]maat.