28-year-old Kerber was officially recognised when she was handed the trophy and a sparkling Tiffany ring.
The 28-year-old was already assured of finishing 2016 at the top of the rankings after Serena Williams withdrew from the WTA Finals with a shoulder injury but it was officially recognised when she was handed the trophy and a sparkling Tiffany ring.
Kerber, looking sharper and more focused than she was in her opening round-robin victory over Slovakia's Dominika Cibulkova, was all smiles after she posted a surprisingly lop-sided victory over the combative Halep, who had looked in ominous touch during her opening match win over American Madison Keys.
"I was feeling very well today. I think that I was moving good and I was going for it when I had the chance. I think that was the key," Kerber said.
For me, I think it's always good when I start a tournament with tight and close matches where I get my confidence.
A finalist at the end-of-season championship two years ago, Halep was brimming with confidence ahead of her clash with Kerber but found the lefthander too good on Singapore's slow indoor hardcourts.
Kerber, electing to receive first, broke Halep's opening service game and despite later dropping her serve and falling 4-3 behind, the German reeled off the last three games in a row to take the opening set after just 43 minutes.
Kerber was even more dominant in the second set as Halep, one of the best returners in the game, struggled to impose her own game on the in-form German, who reached the top of the world rankings when she won the US Open last month.
Two service breaks gave Kerber the advantage she needed and although Halep saved the first two break points she faces with two spectacular winners, it was too little late as Kerber wrapped up the win.
"I had the opportunity to get that first set. I was coming back very well. But, maybe I didn't finish the important points," Halep said.
But she played a great tennis. She's very strong and on her legs she's moving great. She deserved to win.
Despite winning her first two matches, Kerber still has a mathematical chance of missing out on the semi-finals of the elite $7 million tournament after Keys beat Cibulkova 6-1 6-4 in Tuesday's other Red Group match.
That was a little bit better than the first round, said Keys. I'm definitely really happy with how I kind of turned things around."
Although she has lost her two opening matches, Cibulkova still has a chance of advancing if she beats Halep in their final group match on Thursday.
It's frustrating of course because I lost two matches that I wished I could win, but I still have a third chance, Cibulkova said.
It's a big challenge for me. It's my first time playing here. But I can still go into the semifinals.