With the launch of Facebook lite for the regions having slow internet connection they have encouraged users to use their own app to use Facebook. They are also forcing users to use the Messenger, so they are rolling out the lite version of Messenger on emerging markets.
The Messenger lite is less then 10MB, so it will be fast. It provides core experiences such as messaging, sending and receiving photos and links, and receiving stickers. Messenger Lite uses the same bolt logo as Messenger, but with colors reversed. The bolt is blue with a white chat bubble background.
For now, Messenger lite is rolling out to people in Kenya, Tunisia, Malaysia, Sri Lanka and Venezuela and for other countries in the coming months. Facebook apps uses a lot of battery and RAM so, the best way to save resource is to use Facebook Mobile site. If you want to use the app now you can check this link.