"Some time back, I had an Advanced Medical Directive (AMD) done which says that if I have to be fed by a tube, and it is unlikely that I would ever be able to recover and walk about, my doctors are to remove the tube and allow me to make a quick exit," he wrote in the book "One Man's View of the World" published Tuesday.
The book is dedicated to the Asian statesman's views on international affairs but an entire chapter contains his musings on death, religion and other personal issues.
The 400-page work is dedicated to his late wife Kwa Geok Choo, whose death in 2010 shattered the normally stoic veteran politician.
Lee has visibly weakened since then and revealed in the book that despite daily exercise and a disciplined lifestyle, "with every passing day I am physically less energetic and less active."
"There is an end to everything and I want mine to come as quickly and painlessly as possible, not with me incapacitated, half in coma in bed and with a tube going into my nostrils and down to my stomach," he wrote.
Lee, a British-trained lawyer and Singapore's prime minister for three decades who turned it into a high-tech industrial and financial centre, expressed his blunt views on religion in the book.
"I wouldn't call myself an atheist. I neither deny nor accept that there is a God," he said.
"So I do not laugh at people who believe in God. But I do not necessarily believe in God - nor deny that there could be one."
Asked where he drew comfort from if not from religion, he said: "It is the end of any aches and pains and suffering. So I hope the end will come quickly."
Elsewhere in the book, Lee addressed what he considers the biggest long-term threat to Singapore - its low birth rate - and rejected as "absurd" suggestions that his population programme in the 1970s urging couple to stop at two children contributed to the current situation.
Despite a slew of so-called "baby bonuses" to encourage couples to have children, Singapore's total fertility rate last year stood at 1.20 children per woman, far below the 2.1 needed to maintain the native-born population.
Lee, who retired from politics in 2011, blamed Singaporeans' changing lifestyles for the problem and said monetary incentives would only have a "marginal effect" on it.
"I have given the job to another generation of leaders. Hopefully, they or their successors will eventually find a way out," said Lee, who handed power to his deputy Goh Chok Tong in 1990 after 31 years in office.
Lee's son, Lee Hsien Loong, is now prime minister after succeeding Goh in 2004.
Singapore's low birth rate has forced the government to open the country to foreigners, who now comprise a third of the population.
The influx, however, has sparked protests from citizens and prompted the government to tighten immigration flows in recent years.
Lee pointed to the example of Japan, which he said is on a "stroll into mediocrity" as the ranks of its elderly swell due to young couples not producing enough babies.
Japan's reluctance to open up to immigrants will further lead to its decline, he said.
"If I were a young Japanese and I could speak English, I would probably choose to emigrate," said Lee. - AFP
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