Lee's memoirs are definitely a standout from the political memoir genre; they're very readable, and occasionally gripping (especially during the dramatic merdeka-to-separation period). Unsurprisingly, though, he paints his decisions, and those of his colleagues, in the best possible light. The scholar Robert Kaplan once remarked that Lee's memoirs "are contenders for inclusion in Plutarch's early-second-century AD The Lives of the Noble Grecians and Romans"^1, and the comparison is apt in more ways than one. The author is trying to use his account of history to convey a set of lessons, or at least a world-view, to the reader. So that ought to be kept in mind.

The post-separation nation building phase of Lee's career, which you're interested in, was dealt with in the second volume of the memoirs. Unfortunately, Lee made the decision to arrange the book by topic, rather than chronologically. So he'll spend a few chapters talking about national defense, then rewind the clock and start discussing about economic policy, etc. This format lets him go into detail about his government's policy stances and how they evolved over his three-decade tenure, but it can make it difficult to get a historical feel for how Singapore as a whole changed over those decades. Unfortunately, I don't know a better alternative. Most general histories of Singapore spend a lot of time recounting the history up to the separation era, and then zooming through the next thirty years (a period of incredible economic and social change) over the course of the last chapter.

If you want to read a critical but balanced take on the political system that Lee set up, I would highly recommend Cherian George's Singapore: the Air-Conditioned Nation.

^1 Kaplan, Asia's Cauldron: The South China Sea and the End of a Stable Pacific.