I don't think this would happen. Japanese had superior forces and could quickly evolve military tech and weaponry to fight the Russians, as they did the Chinese. And you must remember, the japs took Manchuria not that long ago
I would suggest that you review:
Battle of Lake Khasan
Battle of Khalkhin Gol
The Japanese were, frankly, pitiful regarding the development of new weapons. Take a look at the IJA TOE from 1939 and 1945. Compare it to that of the USSR, UK, USSR, of for a real laugh, the United States. Do the same for aircraft or ship classes. The Japanese played the entire war with the same pair of fives they started with; the Soviets upgraded from a pair of sixes to four aces, the U.S. from a pair of fours to a Royal Flush.
The Japanese Empire was starving for oil. There was not exploitable oil in Siberia, not using 1940s technology, especially 1940s tech available to the Japanese. Attacking the USSR results in massive losses, greatly increased use of fuel reserves, and in short order a collapse of the Japanese economy, and more critically, of the Japanese Army in China.
It is also important to note that, despite the popular myths, the Soviet Union NEVER weakened the Far East Front, even at the worst hours of 1941-42. The "Siberians" that are oft credited as saving Moscow, were as often as not Uzbeks, Kazaks, Chechens, and Siberians who lived within a few hundred miles of the Urals ("Siberia" covers almost 80% of today's Russia, stretching from the Urals to the Bering Strait, a few hundred miles isn't even a dimple)