I would like to reheat chicken/potato soup (heavy whipped cream, cooked chicken, flour, potato, cooked bacon, some salt, and vegetables to name a few ingredients) i.e. thick soup and store it in a thermos (vacuum insulated flask) and eat it at work between 9 and 10 hours later. I work 12 hour shifts, getting a break too brief to use microwave to evenly reheat the soup, breaking at 2, 4, 6, and 9 hours into the shift. I wanted to ask if I could take the soup from the refrigerator, heat it in the oven for 30 minutes (or more/less time in oven) at a higher temperature, then pour into a warmed thermos, to prolong how long the thermos would hold a soup that is warm and reasonably safe. Also, I have a strong immune system, so I might be willing to take on "above average" risk. 
As this is a public site we can not advise other than to follow the food safety regulations of your local area. Assuming that your thermos is high quality and will keep things cold for an extended period of time (10-12 hours or longer), then your best bet is to follow the food safety rules promulgated by various governmental agencies (e.g. USA FDA, UK FSA, etc.). This means that once you have cooked your soup, you should chill rapidly, then only reheat portions as you need them. Do not reheat all, then chill again etc. Generally you need to avoid maintaining temperatures between 4 C and 60 C (40 F to 140 F), as this is the zone where bacteria can easily grow and will make food unsafe in a short period of time. Based on the food safety "rules", the safest way is to pour the cold soup into a chilled thermos (ideally store in the fridge if you can) and only reheat those portions you intend to eat at the time. You would need to reheat to the "safety zone", which for liquids means re-boiling. As you only have a microwave, you would need to reheat, stir and then heat some more to ensure even heating and that the whole soup is thoroughly reheated. I am not sure on the guidelines around if you can keep it above 60 C (140 F) for an extended period so I will make no comment there. 