Comment 33 for bug 273856

> isra@ibex-a-6:~$ echo $XMODIFIERS
>
> isra@ibex-a-6:~$
> ...
> but If I switch session to thai everything work fine. ???

Ah.. So, I've been attacking a different problem than yours.
All my patches were for Thai locale, not English.

Using English locale for Thai environments needs some
cautions, as it's for English, not for Thai.

English locale doesn't set any IM option through im-switch. So,
all apps just use the default null values. For GTK+, the default
input method is "Simple", which is mainly for English and for
European accents composition. (I don't know if it's reasonable
to try to add Thai support to it, but we can try it later.)

Your available choices are scim-thai and gtk-im-libthai. You can
install either on your system, up to your preference, and then
configure im-switch to choose it.

To se what options are available for you:
  $ im-switch -l
  ...
  =======================================
  The available input method configuration files are:
  default default-xim none scim scim-bridge scim-immodule
  scim_xim th-gtk-im-libthai th-xim
  =======================================

In case you prefer gtk-im-libthai:
  $ im-switch -a th-gtk-im-libthai
Or if you prefer scim:
  $ im-switch -a scim-immodule

This needs a new login to take effect.

Note that with gtk-im-libthai, you won't benefit from any input
sequence check for non-GTK+ apps. Those apps will use XIM,
which doesn't check anything on en_US locale. Only GTK+ apps
benefit from it.

If you want to also use Thai XIM upon en_US locale, you will
need to set LC_CTYPE environment to th_TH.UTF-8.
For example, in your ~/.bashrc:
  export LC_CTYPE=th_TH.UTF-8

And finally, note that all GTK+ text entry widgets have an "Input
Method" context menu, which allows you to choose a different
input method on the fly. All described above are for setting the
default one for your session.