I am not stating that for sure if Japan attacked the DEI that the UK, France, USA would jump in. What I am saying is that the UK would see Japan seizing the DEI as a threat to Malaya and Borneo as well as the Australians being quite upset by this. I doubt the French would be pleased by this, and the US was already upset with Japan over China, this would not help. IMHO if the British get involved I think the French will, and even if the US does not get involved the sort of "leaning neutral" that occurred 1939-41 - reporting in clear transmissions sightings of German ships/U-boats etc - would be happening. Yes the Japanese might get away with seizing the DEI without the other powers getting involved but that is making a huge bet.
If Japan goes for the DEI only in 1937 and the British and French jump in, the IJN is in trouble. If the combined European fleets (even absent the USA) beat down the IJN in a Mahanian way, there is no defense perimeter they will have to batter through to get to the home islands unlike OTL. Now Japan faces an increasing blockade and at a minimum economic sanctions from the USA and others. While the Europeans and the USA have not yet rearmed, the Japanese are still doing so and they were barely "ready" by 1941, the carriers and aircraft that gave them a leg up in 1941 are not there yet. In 1937 the severe economic sanctions have not yet started, Japan is not facing a countdown clock to complete collapse of the economy and immobility of the jilitary when their oil reserves run dry. The purpose of the attack in 1941 was to enable continuation of the war in China, not per se war with the Europeans and the USA for its own sake.
The attack on the British and Dutch had the advantages of FIC being occupied and Britain and the Netherlands severely weakened by war/occupation with/by Germany. Even so the attack was a desperation move, and the Japanese knew it - get the oil or stop the war in China were the only options, and the army was not accepting number two. The situation in 1937 is quite different, and while the alliance with Germany was more on paper than anything else, don't forget that in 1937 the USSR would have nothing to distract it from looking at the far east. If Japan is busy with SEA/DEI Manchuria, Southern Sakhalin, and even Korea are going to be much weakened. Nomohan has not happened yet but "Japan" if not the Kwantung Army was not looking for a confrontation with the USSR.