Hamilton is to end his 14-year association with McLaren at the end of this season, joining Mercedes on a three-year deal worth £15million per year.
The move now draws into question his dedication to McLaren for the rest of the campaign, which has six races remaining, starting in Japan next Sunday.
But although trailing Ferrari's Fernando Alonso by 52 points with 150 still up for grabs, Hamilton said: "In terms of the championship, there's nothing to really be gained by analysing the points tables.
"From now on, it's simply gloves-off. As in Singapore, I'll come out fighting, and I'll just be hoping for a better result next weekend."
That follows Hamilton's retirement at the Marina Bay Street Circuit on lap 23 with a gearbox failure when comfortably leading the race, denying him what would have been a third victory in four grands prix.
That, though, had no bearing on his decision to leave McLaren, with Hamilton telephoning team principal Martin Whitmarsh on Wednesday to deliver his answer after being set a final deadline.
Despite being given a decision he did not want to hear, Whitmarsh has no doubt about Hamilton's commitment to the McLaren cause over the final two months.
"He's told me he is," said Whitmarsh when questioned on the matter.
"Clearly there will be cause to be distracted in the next days and few weeks, and we've got to try and protect him from that.
"If I know Lewis he wants to win this year's world championship, he wants to win the remaining six races.
"He's assured me he's a McLaren man for the rest of this year and that he's going to be completely focused on winning.
"So we are going to try and create as much protection for him and the environment in which he can do that."
In all likelihood Hamilton will leave McLaren with just one title to his name in six years of F1 with the team, seemingly an unjust return given his talent and the team's resources.
Nevertheless, Hamilton appreciates the chance afforded to him, and the effort put in for him by McLaren over the years.
"I have been incredibly fortunate to have been part of McLaren and Mercedes since I was 13 years old - I even remember signing my first contract with them," said Hamilton.
"I will be forever grateful for the opportunity they have given me and for their support throughout the years.
"I have had the pleasure of working with a fantastic team of genuine people and would like to thank them for their hard work and support."
Hamilton replaces Michael Schumacher at Mercedes, with the seven-times champion poised to retire for a second time.
However, there are rumours Schumacher could take up Sergio Perez's seat at Sauber in light of the Mexican moving to McLaren, or there may even be an 'upstairs' role for the 43-year-old at Mercedes.