1. Bang Na Expressway – Thailand

The Bang Na Expressway (full name: Bang Na – Bang Phli – Bang Pakong Expressway) is a 55-kilometer-long six-lane elevated highway in Thailand. Bang Na Expressway held the title of longest car bridge in the world from 2000 to 2008. Currently, the bridge ranks seventh in the world in length and is the longest bridge in Southeast Asia.

2. Skyway (Metro Manila) – Philippines

Skyway, officially known as the Metro Manila Skyway System (MMSS), is an elevated highway which is the main expressway in Metro Manila, Philippines.  It is the first fully grade-separated highway in the Philippines and one of the longest elevated highways in the world, with a total length of approximately 39.2 kilometers.

3. Sheikh Mohammed bin Zayed Skyway – Indonesia

The Sheikh Mohammed bin Zayed Skyway, known as the Jakarta–Cikampek Elevated Toll Road, is a 36.4-kilometer-long elevated expressway that extends from Cikunir, Bekasi, to Karawang in West Java, Indonesia.  It is the longest flyover in Indonesia, and the longest elevated double decker expressways in Southeast Asia.

4. Sultan Haji Omar Ali Saifuddien Bridge – Brunei

Sultan Haji Omar Ali Saifuddien Bridge is a dual-carriageway bridge in Brunei. This is the longest two-way bridge in Southeast Asia with a length of 30km. It connects Mengkubau and Sungai Besar in Brunei-Muara District with Labu Estate in Temburong District. 

5. East West MRT line – Singapore

The East West line (EWL) is a high-capacity Mass Rapid Transit (MRT) line operated by SMRT, running from Pasir Ris station in the east to Tuas Link station in the west, with an additional branch between Changi Airport and Tanah Merah stations. It is the second Mass Rapid Transit line to be built in Singapore. The bridge part is 25.7km long, while the total length of the line is 57.2km.

According to Wikipedia.