your new passport arrived to Bkk which day? I think call Thailand post or your embassy and go by yourself and take it better.Probably u will be overstay with red stamp in your new passport and will be very bad for your passport.Also can extend in Bangkok your tourist visa
big mistake before 7days visa expiration u can extend then u will have 1month for making new passport.How u can believe in Thailand just in 13 days everything will be completed(your passports back to you)?
invitation should be thai language right?So this invitation why they dont write on requirements on website Savannakhet Embassy?I saw this on Phnom Penh website but on Savannakhet i didnt see.Also there are many people dont have this invitation and got visa.