He is blogging through his website www.chedet.com, which is named after the pseudonym he used when he wrote articles for the newspapers.
In his profile, Dr Mahathir lists himself simply as the "Prime Minister of Malaysia 1981 – 2003".
Dr Mahathir wrote that the site was dedicated to publishing his writings as and when he was able to pen his thoughts and opinions.
He added that interested parties, including the media, were allowed to reproduce or quote materials published in his site but to credit them to chedet.com.
Comments and feedbacks accompanied by names or pseudonyms were welcome, while anonymous ones and those containing profanities and obscenities would be rejected, he wrote.
His first article, posted at 1.27am yesterday, was on the appointment of judges, in which he posed a few questions on the setup of the proposed commission on the appointment of judges, and how recommendations would be made.
Dr Mahathir wrote that it would be interesting to know the full details of the procedures especially with regard to the role of the Prime Minister in the appointment of judges.
He pointed out that any changes to the appointment of judges required the Constitution to be amended and, as the Government did not have two-thirds majority in Parliament, it needed votes from the Opposition.
"Is the Government proposing to work with the Opposition on these issues, and so display its weakness? Will there be a quid pro quo, a bargain with the Opposition? It would be interesting to see how the PM proposes to deal with this," he wrote.
Dr Mahathir's blog received more than 10,000 visitors by 5pm yesterday. Many commentators welcomed the former prime minister to the blogosphere and said they had been waiting for him to start blogging.
Many said they were eager to hear his thoughts on various issues and welcomed the fact that they could interact with him through the blog.
Some who left comments on his first posting disagreed that it would be a weakness on part of the Government to work with the Opposition to reform the judiciary. They felt that national interest should prevail over partisan politics.
One commentator also asked Dr Mahathir if he thought that the ex-gratia payment for the judges affected in the 1988 judicial crisis was tantamount to contempt of court.