The second on the stroke of half-time was a lethal stab of his left foot after Luis Suarez's slick backheeled pass.
The icing on the cake came five minutes from time on Sunday night at the Benito Villamarin stadium.
Running onto Ivan Rakitic's lay-off, Messi curled his lob over Lopez and into the net.
Only the most partisan or philistine would have begrudged Messi his due acclaim.
"I don't remember the opposition cheering me for a goal," said Messi after the 51st hat trick of his career. "I am very grateful."
Suarez struck Barcelona's other goal in a 4-1 victory that sent the Catalans 10 points clear of second placed Atletico Madrid, who lost 2-0 at Athletic Bilbao on March 16th.
"We had a great opportunity to increase the gap on Atletico," Messi said. "We had to take it."
Betis remain eighth, four points off the places for next season's Europa League.
Messi's latest pyrotechnics increased his league haul to 29 league goals this season. There have been 10 more strikes in other competitions.
With Suarez's 18 goals, their joint total of 47 is more than all but two of the other teams in the division.
With 10 games remaining, Barcelona are in pole position for their fifth title in seven years.
They are also in the last eight of the Uefa Champions League and they play Valencia in the Copa del Rey final on 25 May.