Is there a fee for the 90-day check-in for a non-immigrant B visa in Thailand?

90 day reports can be easy. Two-three minutes in Krabi. Longer in big cities. There is nothing to it in most areas - except a long queue sometimes.

You show up with your passport.

Check your calander. You can go 14 days before or 7 days after the exact date. Pick a convenient date when you might include other activities. No need to pay a fee to some person or outfit you don't know. Immigration does not charge a fee.

Nope, NOT at the immigration office IF you go on your own.

BUT there are many services that will charge you to do it for you.

Where were you charged for a 90 day report?