diff -Nuar xc/lib/X11/imThaiFlt.c xc.thximconv2/lib/X11/imThaiFlt.c
--- xc/lib/X11/imThaiFlt.c	2003-01-06 08:31:25.000000000 +0700
+++ xc.thximconv2/lib/X11/imThaiFlt.c	2003-01-06 08:33:16.000000000 +0700
@@ -626,7 +626,8 @@
         screc.text = 0;
 
         (cb->callback)((XIC)ic, cb->client_data, (XPointer)&screc);
-        if (!screc.text) { return 0; }
+        if (!screc.text)
+            return (unsigned char) *((ic)->private.local.context->mb);
         if ((screc.text->feedback &&
              *screc.text->feedback == XIMStringConversionLeftEdge) ||
             screc.text->length < 1)