Which Japanese military officers helped Ho Chi Minh?

Among some of the more notable officers were:

• Lieutenant Colonel Mukaiyama, reportedly a staff officer in the 38th Army who became a technical advisor to the Vietnamese; killed in combat in 1946. Credited by some as the leader of Japanese forces in Vietnam, and sometimes ranked as a full colonel.
• Major Ishii Takuo, a staff officer in the 55th Division who had commanded a squadron of its cavalry regiment. Supposedly the youngest major in the Imperial Army at the time, he led a number of volunteers to the Vietnamese cause, becoming a colonel and military advisor to General Nguyễn Sơn. He headed the Quảng Ngãi Military Academy for a while before founding the Tuy Hòa Military Academy, and was killed by a land mine in 1950.
• Major Kanetoshi Toshihide, served with Major Igari in the 2nd Division and followed him to join the Viet Minh; he became Chief of Staff for General Nguyễn Giác Ngộ.
• Major Igawa Sei, a staff officer in the 34th Independent Mixed Brigade; he joined Viet_Minh forces, and was killed in action against the French in 1946. The idea for establishing the Quảng Ngãi Military Academy was supposedly conceived by him.
• Lieutenant Igari Kazumasa, the commander of an infantry company in the 2nd Division's 29th Infantry Regiment; he became an instructor at the Quảng Ngãi Military Academy
• Lieutenant Kamo Tokuji, a platoon leader under Lietuenant Igari; he also became an instructor at the Quảng Ngãi Military Academy.
• 2nd Lieutenant Tanimoto Kikuo, an intelligence officer who was originally supposed to remain behind in Indonesia, but linked up with the 34th Brigade to try get home, only to end up an instructor at the Quảng Ngãi Military Academy until 1954.
• 2nd Lieutenant Nakahara Mitsunobu, an intelligence officer of the 34th Independent Mixed Brigade; became a decorated soldier in the Viet Minh forces, and later an instructor at the Quảng Ngãi Military Academy.

Immediately after the Armistice ended the Pacific War, some tens of thousands of Japanese veterans remained in Vietnam, with more in nearby regions. They were actively courted by the Viet Minh, who needed their experience and expertise in their looming war with France. Some 1000 Japanese military personnel thus found themselves on the Vietnamese side, including something like 47 former Kempetai members and/or 46 officers. Though exact numbers should be taken with a grain of salt.

Most of the officers who stayed served as military instructors for the Viet Minh forces, most notably at the Quảng Ngãi Military Academy. They imparted modern military science and training on their students. There were necessary conventional military knowledge such as how to conduct assaults, night attacks, company/battalion level exercises, commanding, tactics, navigation, communications and movements. In addition, they taught them how to fight against a superior enemy through sabotage, ambushes and raids. A few, however, actively led Vietnamese forces into combat.

Those who belonged to the Kempetai were apparently all wanted by the allies. Apart from them, I'm not sure which of the Japanese soldiers were, or were accused of being, war criminals. It seems France primarily wanted to deprive the Vietnamese of Japanese military training and assistance. At any rate, beginning in 1951 these soldiers began to be repatriated, and as far as I can tell none ran into trouble when they returned home.

Sources:

1. Goscha, Christopher E. "Belated Asian Allies: The Technical and Military Contributions of Japanese Deserters,(1945-50)." A Companion to the Vietnam War (2002): 37-64.
2. Goscha, Christopher E. "Building force: Asian origins of twentieth-century military science in Vietnam (1905–54)." Journal of Southeast Asian Studies 34.03 (2003): 535-560.
3. Spector, Ronald. In the ruins of empire: The Japanese surrender and the battle for postwar Asia. Random House LLC, 2008.
4. Kamo, Tokuji. Kwangai Rikugun Shikan Gakkō: Betonamu No Senshi O Hagukumi Tomoni Tatakatta Kunenkan. Tōkyō: Akatsukiinshokan, 2008.
5. Ikawa, Azuhisa "ベトナム独立戦争参加日本人の事跡に基づく日越のあり方に関する研究", 東京財団研究報告 (2005)