The 24-year-old is locked in a head-to-head battle with domestic rival Mark Dry - although only one appears likely to earn the selection nod for Team GB.
Smith needs two throws beyond the 74m London 2012 B standard to be considered.
He threw a season's best 75.63m in March before the qualifying window opened and twice went beyond the required distance at the Olympic trials, winning with an effort of 74.79m, although rules state throws must come from different competitions.
It means he will now travel to a British League meeting in Barnet this weekend knowing it's make or break, while Dry will look to state his claims at the European Championships in Helsinki.
"I'm really chuffed to get that distance and to do it twice plus to come away with the win," said Smith.
"I struggled a bit in the main part of the season but I'm back to where I was in March now and it's looking much better for me.
"Mark's done better than me in a few recent competitions but the trials should be the one that really counts. It's head-to-head but I feel like I made a real impact in Birmingham.
"I've been a bit angry that my early season form hasn't really been recognised, I thought there might be some leniency but there wasn't.
"I can't get consumed by it and I've got to look forward, I'm feeling confident. It was great competing in front of a big crowd in Birmingham and feeling the home support behind you. I just hope I get another chance in London."