ABSTRACT: Paleobiogeography of the Late Paleozoic ammonoids in Southeast Asia is discussed on the basis
 of the fossil records  from Thailand and Malaysia.  The index of faunal resemblance is expressed as 100 C/N1,
 where C is the number of taxa common to  both, and N1 is the total number of taxa (at a specified level) in the
  first, smaller (or equal) of the two faunas or samples compared. The ammonoid faunal resemblance between
 Sibumasu/Indochina  and other regions are studied.  The fluctuation of the curves between  Sibumasu and
 several regions supports the previous opinions that  the Sibumsu terrane separated from the margin of
 Gondwana-land in Early to Middle Permian. However, the faunal resemblance between Indochina and
 South China does not show close  relationship from Pennsylvian to Middle Permian. This result is opposed
 to the previous opinion.