RR, my guess seems to be right! Pallavi and TMS' portions are within the Sivaranjani scale. 2nd charanam has an extra N2. The last charanam has loads of chromatic notes and is good fun to play!
Here's a rough notation of the song.

uuvp.JPG
uuvc1.JPG

uuvc2.JPG

uuvc3.JPG