Sundaland covers a small portion of southern Thailand (provinces of Pattani, Yala, and Narathiwat); nearly all of Malaysia (nearly all of Peninsular Malaysia and the East Malaysian states of Sarawak and Sabah in northern Borneo); Singapore at the tip of the Malay Peninsula; all of Brunei Darussalam; and all of the western half of the megadiversity country of Indonesia, including Kalimantan (the Indonesian portion of Borneo, Sumatra, Java, and Bali).  

• The Nicobar Islands, which are under Indian jurisdiction, are also included. Sundaland is bordered by three hotspots.  
• The boundary between the Sundaland Hotspot and the Indo-Burma Hotspot to the northwest is here taken as the Kangar-Pattani Line, which crosses the Thailand-Malaysia border.  
• Wallacea lies immediately to the east of the Sundaland Hotspot, separated by the famous Wallace’s Line, while the 7,100 islands of the Philippines Hotspot lie immediately to the northeast. 

Source: http://bsienvis.nic.in/files/Biodiversity%20Hotspots%20in%20India.pdf