For address information you should write your permanent address in France. Then select the option permanent address is NOT same as your current address and then it will open a second address inputs. There you input the accommodation in HCMC you will stay for three visa process. As for accommodation in Thailand, input your intended address in Thailand.
You can ask for a residency certificate at your embassy. My embassy (Mexico) helped me with that and I had around 3 weeks living in Thailand. In my case they asked me for the TM30 form, a letter for the purposes I need the certificate for (vehicle registration and drivers license) and a copy of the rental contract with no length requirement (should include landlord contact information and copy of his/her id).