I dunno.
If WW2 ends about the same way as in OTL, then America will be very worried about the Russians doing better in the Pacific. Maybe we'd prop up an independent Japan?
Well, it's hard to see them continuing the China war through 1945 if the US oil embargo remained in place, and I've seen it argued fairly convincingly that funding the war + reduced trade was leading to a serious hard currency crunch. Home industries ran on coal, not oil, but there were other rather materials they imported, and the navy and the mechanized bits of the war in China ran on oil. So, if all is as OTL, I'd expect some sort of crisis of sorts before '45 - which is why the Japanese did what they did OTL.
So, if we want the Japanese to keep their grubby hands off the Phillipines, Indonesia, etc., we need more than "don't attack the US". Not invading China in the first place is probably for the best: it's not like Chiang's army had a snowball's chance in hell of throwing them out of Manchuria.
If that's too hard, at least avoid joining the Axis and grabbing Indochina: this may avoid the embargo, although they're still probably going to lose their most-favored-nation trading status. Still going to be running into that hard-currency problem, but by the time it really starts to bite the US is probably going to be going all guns vs. Germany, and a guided tour of a US facility producing battleships like sausages is going to cool any inclinations towards joining the war on the German side.
(Continuing with the "Japanese still invade China" scenario)
Post-war, the Japanese are going to be under a lot of pressure to vacate China, and will be in a state of "maximum danger" from about 1945 to 1950, by which time US anti-Communism should be beginning to trump pro-Chinese sentiment - "if we pull out of China, the Reds will take over!" will be seen as a more acceptable excuse in McCarthy's america than in Roosevelt's. The trouble is, of course, that the Japanese are going to be in economic difficulties well before then, and they don't have a Marshall Plan or OTL's relatively free access to US markets - as allies against the Reds they might still get it eventually, but they're not going to in 1945. Probably at this point they're going to be struggling to find a way to "declare victory and pull out", and a desperate search for a useable puppet will be under way...
(Nightmare scenario: Japanese pull out, and the US moves in to support a theoretically anti-communist government. Vietnam X 20 follows).
Anyhoo, if the Japanese manage to pull out without being, say, kicked out by the Soviets, an even longer Japanese occupation probably improves Mao's chances: the Japanese may end up supporting the Guomindang as the least bad alternative (although will Japanese support be so poisonous that Jiang dare not take it?).
Bruce