I take Trata to mean Traka! I play this totally on Tabla( Dayan , Right hand drum ). I use three fingers of my right hand. Stroke the Tabla( going from left->right as flat as possible ): 1) Starting with the ring finger followed by middle and index fingers, one at a time in quick succession. This completes Tra 2) for Ka: change the direction of the stokes and hit the Tabla with ring/ring+middle going from right->left. If you use 2 fingers, use both at the same time to produce only 1 bol.
This completes my "TraKa"
This is slightly tough for beginners, especially clarity!! You can start in slow tempo and then gradually speed up, just like other strokes which contain more fingers( like TitaKita, etc ).
TraKra is a different bol than TraKa. If you refer to my previous main of "TraKa", only modification would be reqd in the 2nd part. In Kra( just like Tra ), use 3 fingers instead of 1/2. From right->left, hit middle finger followed by ring in quick succession to create 2 distinct bols( k r )