Is there any way to redraw tmux window when switching smaller monitor to bigger one?

tmux limits the dimensions of a window to the smallest of each dimension across all the sessions to which the window is attached. If it did not do this there would be no sensible way to display the whole window area for all the attached clients.

The easiest thing to do is to detach any other clients from the sessions when you attach:

tmux attach -d

Alternately, you can move any other clients to a different session before attaching to the session:

takeover() {
    # create a temporary session that displays the "how to go back" message
    tmp='takeover temp session'
    if ! tmux has-session -t "$tmp"; then
        tmux new-session -d -s "$tmp"
        tmux set-option -t "$tmp" set-remain-on-exit on
        tmux new-window -kt "$tmp":0 \
            'echo "Use Prefix + L (i.e. ^B L) to return to session."'
    fi

    # switch any clients attached to the target session to the temp session
    session="$1"
    for client in $(tmux list-clients -t "$session" | cut -f 1 -d :); do
        tmux switch-client -c "$client" -t "$tmp"
    done

    # attach to the target session
    tmux attach -t "$session"
}
takeover 'original session' # or the session number if you do not name sessions

The screen will shrink again if a smaller client switches to the session.

There is also a variation where you only "take over" the window (link the window into a new session, set aggressive-resize, and switch any other sessions that have that window active to some other window), but it is harder to script in the general case (and different to “exit” since you would want to unlink the window or kill the session instead of just detaching from the session).

You can always press CTRL-B + SHIFT-D to choose which client you want to detach from the session.

tmux will list all sessions with their current dimension. Then you simply detach from all the smaller sized sessions.

A simpler solution on recent versions of tmux (tested on 1.9) you can now do :

tmux detach -a

-a is for all other client on this session except the current one

You can alias it in your .[bash|zsh]rc

alias takeover="tmux detach -a"

Workflow: You can connect to your session normally, and if you are bothered by another session that forced down your tmux window size you can simply call takeover.