Malaya is too vulnerable, and it takes too long to secure. HK is far stronger for your later-game strategic defense (free NB), hidden square)
To win as Japan you have to 1) keep the interior seaway open in order to 2) keep the land front alive. You will also want to kill India. If these goals are not attainable after turn 6, you are about to lose.
You can keep the land front alive more cheaply than you might think; normally we would want 2-3 factories pumping out mechs and tanks but that’s 50$ a turn without building any bases, planes or sea units. But if the difference is a collapse, then infantry and artillery are fine for 60% of the price.
The game is going downhill for Japan as soon as you lose the arms race against the USA, because SZ 6 will no longer be a safe place to put units pretty quickly (USA KJF 6+). In order to stop this from happening, you need to deter the USA, which means allocating more money and units to defense (objective 1) rather than killing india (objective 3).