It is good advice from davureborn to go to immigration a week before to ask about maybe new requirements.
I used this list every year and no issues (and as always bring more then you actually need
)
1) TM 7 Immigration Form
a. Photo Size 4x6 to stick on TM 7
2) Copy Passport
a. Copy Face Page
b. Copy last Non ? O
c. Copy Last Entry Stamp into Thailand
d. Copy Last Extension of Stay
e. Copy TM 6 Departure Card
f. Copy last 90 day report
3) Copy Marriage Certificate (Khor Ror 3) + Original
4) NEW Khor Ror 2 obtainable from Amphur (Max 1 day OLD)
5) Copy ID Card Wife + Original
6) Copy Tabien Baan Wife + Original
7) Family Photos
a. Couple sitting on Bed
b. Couple outside with House Number clearly visible
c. Couple sitting in Living Room
d. Couple sitting outside House (near front door)
Hand drawn Map to the House (Complete with GPS Coordinates)
9) Bank Book Fixed Deposit from Bank on day of visit to Immigration
a. Transfer THB to Fixed Deposit account on day of Extension
b. Update Bank Book @Bank Branch on day of Extension
c. Bank letter Fixed Deposit obtainable from Bank (Min. Amount 400.000 THB)
d. Copy All pages of Bank Book