We are looking at a new apartment near Chaweng beach, long term rent. Landlord says it's ok for a dog but the juristic office is not sure. Rosie is 2.7 years and quite calm. Anyone rented with a dog in Koh Samui? What did they say?

Yes, ask the juristic office in writing before you sign. Some buildings say dog ok but limit size or ask a deposit. Get it in the contract, not just a voice promise from the landlord. In Samui many places are fine, just check first.