I'm not sure if this means they are exactly 'building' a data center, but the Data Center Journal reports that Google is "transferring servers" to Korea in order to better comply with local regulations.
Other things I have read here and there, certainly show Google's interest in the global market, underwater fiber to Europe/Asia and peering arrangements.
Check out the Data Center Journal article here.
Google's Fiber (older story) here
Google jobs: Strategic Negotiator-Global Infrastructure