'It is part learning, part nostalgia,' said political analyst Liew Chin Tong, adding Mr Lee wants to feel the pulse of a radically changed country.

'He is intensely curious, he wants to assess how the Malaysian future will shape up and how that will impact on Singapore,' Mr Liew said.

The last time Mr Lee visited Malaysia was in 1999, when then deputy prime minister Anwar Ibrahim was in jail and the country was caught in the throes of the Reformasi movement.

Mr Lee had driven into the country from across the causeway in southern Johore state, praised the road and other infrastructure developments, admired the Petronas Twin Towers, and before leaving famously pronounced that the sacking and jailing of Mr Anwar 'could have been better handled'. That statement irked his arch-rival, former prime minister Mahathir Mohamad, and worsened the already stormy relationship between the two leaders.

Mr Lee will not be meeting Dr Mahathir nor opposition leader Anwar Ibrahim, who as in 1999 is again facing a sodomy charge, with the controversial trial opening on July 1.

Malaysians have always been divided over Mr Lee, with many admiring him for turning the colonial outpost of Singapore into a thriving financial centre, while others criticise him for 'walking away' with 'our' Singapore. He also earned Malaysian envy for turning Singapore into a shining example of what Malaysia could be, a point constantly used by opposition lawmakers to rile the ruling National Front government.

Mr Lee, who is minister mentor in Singapore, will meet friends and visit places he frequented as a Malaysian politician and lawmaker.

A highlight of the visit is a meeting on June 13 with Lim Guan Eng - the only ethnic Chinese chief minister in the country, who heads the administration in Penang state, which he wrested from the National Front last year. Mr Lim, who says the National Front is deliberately not helping Penang develop, has visited Singapore several times and asked Mr Lee for help with investment.

The outcome of that meeting and another with Nik Abdul Aziz Nik Mat, the most revered Islamic leader in the country, will be keenly watched by the National Front, analysts say.

'We can also view Mr Lee's visit as an endorsement for Mr Najib because Mr Lee believes if Malaysia is unstable it would affect Singapore,' Shamsul Baharuddin, National University of Malaysia political scientist, said. 'Mr Lee knows that events that shape Malaysia will also shape Singapore. He is visiting to know things at first hand.'

Singapore-Malaysian relations improved considerably after Abdullah Badawi took over following the retirement of Dr Mahathir in 2003.

Mr Najib has said he wants to put the relationship on a better footing, and expand trade and investment.

The Malaysian Insider, a politically connected website, said in a June 3 editorial that Mr Lee's visit is to learn how Islamists and secularists came together to capture five National Front-ruled states.

'That feat shocked Singapore, which has only known PAP rule since independence, just like [National Front] rule in Malaysia,' it said, referring to the dominance of Mr Lee's People's Action Party.

A former editor with the New Straits Times daily agreed.

'Mr Lee wants to know if a similar revolt can happen in Singapore, which shares a similar repressive political culture as Malaysia,' he said.