This building is a Declared Monument and is open to the public.
The AMO website states:
"Located in the south-west corner of Yuen Chau Kok, Wong Uk Village was founded during the reign of Qianlong (1736-1795) in the Qing dynasty by the Wong clan from Xingning county in Guangdong. In the 19th century, the village became a major trading station for travellers and traders plying the route between Guangdong and Kowloon and prospered until the late 19th century. Most of the village's old buildings fell into ruins and were later demolished when Tide Cove was reclaimed for the development of Sha Tin New Town. All that remains is the Old House, built around 1911 by Wong Tsing Wo, a 19th generation descendant. The old house is two-storey green-brick structure with fine mural paintings and traditional decorations. It now stands as the reminder of the history of Yuen Chau Kok."
Photos, opening hours and more information can be found on the AMO website: http://www.amo.gov.hk/en/monuments_39.php