It's amazing how many people don't actually know this. Check out this short video from the Office of Road Safety on merging if you have any doubts.
Hot tip: Give way to the vehicle in front of you REGARDLESS if in left or right lane.
Also worth noting, the penalty for failing to merge correctly has increased to 2 Demerit Points and a fine of $100.
Watch the video for more info, and check out www.ors.wa.gov.au for more road safety info.
Shoutout to Khya for alerting us to this video.