Hi, a post just to let you know how it turned out for me at the Thai embassy in Hanoi.
All the staff is very nice, I went there pretty early(maybe 9am). Nobody was there, I gave the tickets flight in/out from Thailand, financial proof ( from last month), the form and the 40dollars. I previously had a 3months visa in my Belgie passport, this time I gave the French one and the lady said nothing except that I have to comeback on Monday to get it back.
Have a nice day and thanks everyone for your help!
TLDR : Answer Summary
The user shared their positive experience at the Thai embassy in Hanoi, where they applied for a visa using their French passport. They provided the necessary documents, including flight tickets and financial proof, and noted that the staff were friendly. They were informed to return on Monday to collect their visa.