Dr Mahathir Mohamad still complains about how things are being done in Pakatan Harapan, according to PKR president-elect Anwar Ibrahim, but he says he often tells the prime minister that these rules are necessary to keep up with the times.

"Some of these rules, (he asks) 'Why this', 'Why that'... he continues to do that," he said in an interview with ThaiPBS.

Interviewer Suthichai Yoon also asked Anwar if Mahathir cautions him over their differences.

"He did. For example, (he says we are) a bit idealistic, too democratic or too liberal. I said, 'The world has changed, Mr Prime Minister, we are no longer in the 1980s. 

"We must have the confidence and trust that we can build (the country back up), but of course it requires strong institutions," he said.

Anwar said he believed that Mahathir had accepted the necessity of reforms after personally witnessing the decline of the country.

"Some people may attribute (these problems) to him, but I would say he could not have imagined that it would have got to this extent."

Mahathir served as the fourth prime minister from 1981 to 2003.

He returned as the seventh prime minister after the May 9 general election following a successful alliance with then-opposition pact Pakatan Harapan, which included Anwar's PKR.

In Mahathir's first stint as prime minister, he sacked Anwar as his deputy in 1998, and had him jailed due to disagreements over the running of the country.

Mahathir was also accused of being a dictator by his critics in the past, due to his jailing of his political opponents.

'Not impressed at first, but I am now'

Anwar told ThaiPBS that he was amenable to an alliance with Mahathir when the latter first approached him with an olive branch, but was not too impressed.

"But I saw how hard he worked, how difficult it was for him.

"In the first few rallies, every speaker before him would say how Mahathir had imprisoned them, or (had them) assaulted... he had to swallow these things.

"Until he end of the (14th general election) campaign, he was there nightly. He was very tough. I think people do give him credit, and I do too," he said.

Anwar added that Mahathir himself suffered by siding with the then-opposition under the administration of Najib Abdul Razak.

Read more: May 9 phone call – Anwar reveals what silenced Najib

Now, Anwar believes he has a "good" relationship with his former nemesis.

"I don't meet him that often, but we have private exchanges once every fornight. I have long chats with him."

These chats, Anwar said, are on policy matters and issues affecting the country.

Asked how he was preparing to take over from Mahathir in the future, Anwar said he is being kept abreast on the country's affairs with the former's blessing.

"The prime minister has been kind. He has allowed the ministers to brief me and talk to me," he said.