This development was earlier reported 12 weeks ago while on beta phase, David Marcus announced on his Facebook Page that you can now send SMS via Facebook Messenger on Android.
In his words,
A lot of Android texting apps didn't keep up with the evolution of messaging, so we felt like we truly had to make Messenger the best SMS client for Android. As a result, in addition to having a fully integrated app for all your messaging,
you're now able to send voice clips, stickers, and even share your location over SMS on top of standard texting features. You will now also enjoy all the things you've come to love about Messenger for all your messages, including chat heads and more.
How Can You Do This
>> Just go to settings, select “SMS”and turn on “Default SMS App.” This will ensure all your SMS conversations appear in Messenger as purple threads, alongside your blue Facebook chats.
Note that standard SMS fees still apply.