The move south was the desperate act of the Imperial Council in the aftermath of US embargos that threatened the ability of Japan to continue the war against China, not just the result of a 'black eye' given them at Khalkin Gol or Lake Khasan, for those losses made little impression on the high command.
Japan was already out of funds for continuing the war and the required expansion of forces to deal with the US, Dutch and UK/CW in the Pacific. The move to seize the SEA resource region was the result of their fear that the Germans would defeat the USSR by the end of 1941 and a general peace that ensued would leave the UK, French and Dutch free to defend their colonies and possessions in the Far East.
The risking all in face of US intransigence formed the basis for what was taught Japanese school children postwar, that Japan 'had to go to war against the USA, which had directly threatened Japan's existence' or words to that effect. Thus, WWII was forced upon the Japanese Empire by the nefarious Americans.
I am not making this up.
I attended the Korean Air Force Staff College with a Japanese Air Self-Defense officer, who despite being rabidly pro-American (he later attended U.S. Air Force Air War College), believed exactly what you say here.