Cognomen ฤทธิวาจา (Ritthivajar 
, ฤทธิวาจา , Rittivaja ) , in the world, is a very rare last name. The surname ฤทธิวาจา is characteristic of South-eastern Asia, particularly Thailand, where it is a rare surname. Much less frequently, ฤทธิวาจา is the forename as well as the last name.