From Owner/Seller
Some property owners are now offering financing to buyers of Thailand villas, bungalows and condominiums as a way to sharpen interest in their Thai property. The buyer and owner/seller then sign both a purchase and a sales agreement and a promissory note.
Assure yourself that the seller is actually also the owner of this property. Ask for a copy of the title deed and check carefully at the land office with marina one residences showflat the assistance of your Thai wife or partner. The land office can also tell you if this property is actually mortgaged or not.
Most likely if the seller cannot provide you with a genuine title deed, then the property is mortgaged and the land title is kept at the bank or at the money lender as a security for the monthly payments.
In case you are engaging a real estate agent to assist you find your dream villa, then you can let them know you require financing. Most likely they will have a few listings where the sellers are offering payment terms.