WHEN it comes to the local music scene, Canto-pop icon Andy Lau Tak-wah is undoubtedly king. But in the bad and dangerous pop world outside it is Emperor Michael Jackson who gloriously reigns. Lau was billed to perform a series of well-publicised August concerts in Singapore under a sponsorship agreement he recently signed with Pepsi. But that was before Jackson finally decided to tear himself away from the dodge'em cars and pin-ball machines of Never-neverland, his theme palace in the Californian desert, and get round to touring the world again. Now that Jackson's management has deemed that he will ''do'' (Michael, we'll have you know, never ''performs'') Singapore in August instead of June as the local promoters had requested, Lau's dates have been scuppered. According to a spokesman for the organisers (for the first time the two leading Singaporean promoters have joined forces to bring Jackson to the City State) they were ''in no position to renegotiate with Michael Jackson, so we had to make Andy Lau postpone his concerts''. We understand the Canto-pop king, whose tight concert schedule is planned months in advance, was far from happy about the abrupt change made to his plans. And, according to local reports, Lau's deal with Pepsi wobbled a bit as a result. But things have now been smoothed over and Lau will fulfil his Singaporean concert dates in the latter part of 1994.