Hi there, can I extend my 30 day entry by 8 days at the immigration office? I have an air ticket out that's 8 days after my entry expires. Thanks.

7 days maximum to leave the country. 1,900 Baht fee.

So can I get 7 and then overstay for 1?

They will likely provide but at times require an exit within 7 days to do so. A quick border crossing/return might be about the same cost and get you 15 day visa exempt entry.

Ok thanks for the info