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!