combined character displaying each as different character

[vijayavelanr]

Hi Vurtun,
Need you help in understanding if I'm doing the right way. Thanks a lot.
I'm trying to display the below tamil character which is a combination of 2 unicodes. but they get display as separate ones. can you pls clarify if I'm using it correctly.
it is interpreting as 2 different characters instead of combining them.
wrong print: த ோ . even shorter as shown in below picture. I'm using windows default latha.ttf font for this.
correct should be like this தோ

           char * f = calloc (7, sizeof(char));
            f[0]=224;
            f[1]=174;
            f[2]=164;
            f[3]=224;
            f[4]=175;
            f[5]=139;
            f[6]='\0';
        nk_layout_row_static(ctx, 30, 80, 1);
        if (nk_button_label(ctx, f))