The Landlord Notification Receipt, or TM.30, is a very important document that all foreigners must have while staying in Thailand. It is the responsibility of your landlord to notify Immigration of any foreigner staying on his property within 24 hours. If your landlord has not done this, he will have to be fined 2000 baht per adult in that property.
The TM030 and its underlying laws are about the obligation of a landlord (or house master, possessor, manager) to report the stay of a foreigner (non-Thai national) in his/her property. All foreigners staying in Thailand and their hosts should be very well aware of this.
Immigration just changed some practicalities that can affect a lot of foreigners staying in Thailand. Article 37 stipulates that a foreigner residing in Thailand should report to immigration if he/she visits another province for more than 24 hours. This would mean that a short weekend trip from Chiang Mai to Chiang Rai would cause a lot of red tape, even when you have already done all the basic TM.30 reporting.
Your landlord or landlady can either do this online or visit Immigration, however they may ask you to go with them.
For more information visit Thailand immigration bureau website: http://bangkok.immigration.go.th