In his book The Inner Game of Chess GM Andy Soltis commented than Tan made errors in calculation that resulted in three missed wins. Looking at the game with a modern engine I am not so sure that 1) finding the forced wins over the board would have been all that easy and 2) Tan was getting into time pressure and likely didn't have time to do a lot of deep searching. Instead he chose moves that were easier to calculate, but they were not as forcing and as a result, he drifted into equality then lost on time. The point is, Tan's play wasn't a blunder-filled blown win that some seem to think it was. For whatever reason, he played a series of second best moves that resulted in a drawn position before losing on time. It also shows just how hard GMs, especially world champions, are to beat. They don't just roll over and die.
By age 11, he was beating his brothers which often lead to literal fights with the loser literally throwing the chess set. But the Tan brothers, Lian-Ann, Lian Quee and Lian Seng were good enough that they kept the Singapore Chess Championship in the family for seven consecutive years from 1961 to 1967 and in school the chess team included Lian-Ann's brother Lian Seng and the team was unbeatable.
Lian-Ann Tan went on to study accountancy at the University of Singapore. He gave up competitive chess and became a "social player" in 1992, saying he came to the realization that he "wasn't good any more." Tan stated that was when computers were coming in to the picture and people were starting to learn from them, but he didn't have time to study because he was too busy with his business.
In his competitive days, he was awarded the IM title in 1973 after qualifying for the Interzonal at Petropolis where he finished tied for last in places 16-18. Prior to that he had played in the Australian Championship at Perth 1962/63, the World Junior Championships at Vrnjačka Banja 1963 (won by Florin Gheorghiu) and Barcelona 1965 (Robert Huebner won).
He won the championship of Singapore six times and shared first at Hong Kong, the East Asian Zonal in 1972. At the Zonal tournament in Melbourne 1975 he finished second behind Eugenio Torre, but only tied for 18-20th at Manila in 1976.
Tan also represented Singapore four times in Chess Olympiads in 1968, 1970 and 1972 (all at first board) and in 1992 at third board.