The long-roofed masjid is unique and vernacular to the region once known as the Langkasuka Kingdom. The long-roofed masjid has a rectangular plan with long ridges and distinctly differs from the pyramid-roofed masjids commonly found throughout Southeast Asia. In considering the sustainable development goals (SDG) for communities and heritage, the long-roofed masjid should be included in preserving the identity and culture of the region. The paper highlights the character of the long-roofed masjid to expose and preserve the form that is no longer recognized or associated as a vernacular form in the region. The objectives are to underline the characteristics and form of existing vernacular masjid and houses to deduce the regional identity of the Langkasuka region. The analysis dissected the architecture of long-roofed masjids into several typologies according to the roof design. The samples for the study are collected through site visits and supported by literature reviews, and a visual analysis is performed to extract the unique characteristics of the masjids. The results suggested that cultural sustainability is manifested in the use of the balai lintang and serambi in the long-roof masjid. In addition, environmental sustainability is seen in the architectural components and construction incorporated. Due to its cultural and environmental significance, the long-roofed masjid architecture needs to be preserved as a manifestation of the beliefs, way of life, or culture of the Langkasuka kingdom. The legacy of the long-roofed mosque from the area can reveal the identity or ancestry of a community that lived there in the past.