When you checked in at your hotel , you gave them your passport , correct ? . They then register you .. it’s their responsibility.. and how did immigration contact you anyway ?
certainly if your flying in and out of the country ( Thailand ) you can come and go as many times as you please . I note your Spanish? .. so currently you will get 60 days on entry + 30 extension, that’s your 90 days as you know .. fly to Cambodia stay just a couple of days if you like
And fly back in and start again 60 days + 30 days .. you could in principle do that forever or certainly under the current rules , Flying is the key here , not by road .
You might get questioned about finances and as to why you keep coming and going ? .. ( they immigration don’t like to think your working illegally) ..
It’s not true , you can get a 6 month ‘ holiday ‘ .visa
You need to show you’re financially secure, where she will stay , guarantee she won’t be participating in any work what so ever and that you’ve been in a relationship.. photos , correspondence etc .. you can do this at the American embassy in BKK ,, or via an agent ( easier with an agent ) but cost around £500 ( sterling ) .