Does anyone know which documents I have to show to immigration after 28 days expired for my first time non immi o visa request?

If you have already done all the paperwork for an extension based on marriage and they told you to come back in 28 days, then all you need is your passport, unless you have been notified that there is a problem.

For a 12 month extension for marriage to a Thai you just show up with your passport.

You may wish to ring the immigration office before making the trip, in case the extension has not been approved yet, to avoid the possibility of a wasted journey. I guess it depends on how far you live from your local immigration office. For me it's a 250Km round trip....

Edited January 6, 201511 yr by mxyzptlk