Just entered Thailand on my one year B Visa non immigrant multiple type but immigration officer stamped on my passport only 45 days stays as TR Visa and crossed on my visa as Last entry 18th April 2023 but my visa valid till December 21st 2023. He thought it was single entry tourist Visa.

I just seen after come out from the air port.

I supposed to get 90 days to stay ok same as before but now allowed me only 45 days and cross by a pen on my one year Visa.

Please advise me where and how to solve this issue?

Just to confirm --

(1) even though I got our SETVs for the entire family by myself, in order to do 30 day extension at Chiang Mai immigration, the entire family needs to go, correct?

(1a) My understanding is that the 30 day SETV extension is a short wait at immigration - so short that I could take the kids in at 3:30 on a Friday and potentially still be seen that afternoon?

(2) regarding overstays for children, after the expiry of our SETV, we have a few trips planned where we'll return on exemption stamps and, if we decide to stay longer, will look at an ED visa. Am I reading correctly here that many people let their children overstay, and I would neither need to ensure that we all left for runs to get new exemption stamps nor would I need to worry about finding an ED visa that would also process O visas for the kids? I'd obviously rather do it proper, but if I could justify a few kid-free vacations to get fresh stamps, I'd rather do that :p

Thanks!