Air BnB on retirement

Regardless of the visa type of the owner, any rental for less than 30 days is illegal in Thailand. Should you want to do it legally you would need an hotel licence but you can't obtain it with a retirement visa.

Then if you want to rent for more than 30 days you can do it providing you declare the people to immigration under the form TM 30 and you declare every year your revenue to the fiscal authority on which you will have to pay a flat tax of 30% . In this case your little business is completely legal.

As a foot note, more and more condominiums are prohibiting the short term rentals for safety reasons and peacefulness of the resident owners. And contrarily to the affirmation of the precedent replier, at least in Chonburi province, police and immigration do some crack down mainly after having been denounced by other owners or else, or thanks to the renter going to immigration for visa prolongation and not having valuable TM30 .

As said above, nothing is impossible in Thailand and many do it....... At their own risks....