How to define a Sorting order sequence for UTF-8 Sinhala Language in Hibernate Search

[indika.indikak.dmsswt.com]

I am using Hibernate Search for a tri lingual application which has over 5 million data volume. I am very impressed with the performance of the search operation TXN to the Hibernate Search, however I was unable to sort data stored in UTF-8 Sinhala language. The problem seems that there is no way I can define the sorting order sequence for the Sinhala. (Like in English A,B,C,D…etc)

Any ideas?
Thx