can i rent trailers for moving from apartment to aparment in thailand, bkk specifically? thanks

Never heard of it, but there are local guys with a van who will help you for a small fee.

approach your local motorrcycle taxi guys. one of them will have, or know somebody who has a truck. they will also provide labour. everytime i have moved this is the route i have gone.

barring that look around your soi for a parked pickup truck with a phone number on it.

they can be an invaluable service if you treat them well, doubling as messenges, bill payment serice, food delivery and pickup etc. some are very happy to do odd jobs, gardening, painting etc around the house.