I arrive into Bangkok from Australia at 1AM for a one months holiday I do not have a visa as I understand I am entitled to a visa exemption for my visit. The consulate website states that a visa exemption on arrival is for 28 days stay. however I have been reading on this site that a new update to immigration rules I can get 30 days stay. Does anyone know if it is actually 28 days or 30 days duration for a visa exemption stamp.

As as my flight will arrive after midnight (1 AM ) next Wednesday will immigration count the visa time days from the Wednesday or will they count the days from the day before ( Tuesday,) . does immigration adhere to the principle that after 12 midnight that a new day has begun ?

You get 30 days that includes the date you arrive. It has been 30 days for a long the entries have been allowed. The consulate website is wrong or they are saying 28 days to insure people don't miscount their days.

If you arrive after midnight you will be stamped in for the new day.

Yes 30 days including the day you arrive.

Been that for a long time.

Now you can also extend your visa-exempt permission to stay for an additional 30 days without having to leave the country.