Phrase pattern
Who → does what → ที่ → where
The place goes at the end after ที่, which covers at, in and on
who+does what+ที่+place
Several rules work together in this pattern: who → does what → what; a place comes last, after ที่.
The person studies at home
The friend sleeps at the hotel
The police officer wakes up in the room
Practice with this pattern changes the words each time. They come from the words you're learning.
Kai says
The vowel เ is written before its consonant, but spoken after it. Your eyes see the vowel first; your voice starts with the consonant.