How does a IT Admin block chatting in a company?

There are network control offerings like WebSense. You could use a service like OpenDNS, assuming you get reliable service to the closest resolver (Singapore).

You can use a router, firewall, other network appliance, or server that can block domains, URLs, ports & protocols.

You'll have to make sure users do not have administrator accounts. You can then keep them from installing chat clients or anything else, and keep them from getting around any filtering you might use.

Just heard about this application firewall that it is kicking up a storm. Don't get the latest updated software, use the older stable one that may be already preinstalled. Otherwise, use your juniper routers to control this type of bandwidth use.

First, as seanferd pointed out, use OpenDNS to block the sites, then use a firewall rule to block ports which are used by the chat clients.

We use DNS Redirector to block all the various chat sites, prevent downloading of new IM clients, and prevent logging into IM clients.

The advantage over OpenDNS is you can allow some users to bypass this restriction on a daily, or temporarily basis (with a password or active directory integration), and you can log internal DNS requests to determine (with per-client detail) who is abusing policy.

I should note; before implementing a technology solution to block this nonsense, you should implement a written policy on acceptable computer use and employee's job responsibility. All employee's should sign this, so it's easy to terminate them when they disregard it.