Participle form: Santang, samaanang, etc.

F. Mason (1868) explains the following as a participle form of "asa" (i.e.,
to be), but it seems to me that it could instead be the participle form of
"sammati", and a few dictionary entries seem to suggest this as well:

      Pathamapurisa  |  Majjhimapurisa   |   Uttamapurisa
      ---------------------------------------------------
eka    Santang          santii             santo
bahu   samaanang        samaanaa           samaano


Now, I find that I am without any kind of lexical source to really affirm or
deny this: is "santo" (etc.) a participle of "asa" or of "sammati"?   If
anyone has a textbook that definitely gives a different conjugation for the
participle of *either* "sammati" *or* "asa" this would be very useful to me.

Thank you,

E.M.

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