Condo unit sale agreement content
Maybe the intention is that when foreign ownership in the condominium is not available at the time of transfer of ownership it can be transferred to your Thai wife as a Thai owned condominium. But this does not work because whether the condo is registered in your name, both your names or in your Thai wife' s name it will count for the land office as foreign freehold ownership because your wife is married to you, a foreigner (info issued by the Thailand land department). So, even when the condo unit registered in your Thai wife's name the apartment unit will still be considered foreign owned because of her marriage to the foreigner and you/ she must therefore comply with section 19 of the condominium act, (read more...)
Mortgage option and foreign ownership
The 'and/or' option could also relate your own choice, that when you try to get a mortgage the (Thai) bank may request that the unit is registered in your Thai wife's name as a personal property (to achieve this you need to follow the same procedure as with a land purchase by a Thai married to a foreigner) before they are prepared to provide finance for the condo. But I'm not sure about that. The probable reason would be, when the condo is acquired as a marital asset you and your Thai spouse must comply with section 19, i.e. you must have remitted foreign currency into Thailand and exchanged the amount in Thai baht (unless you are a resident in Thailand or qualify under other grounds of the condominium act section 19). With a financing of a jointly owned condo in Thailand you nor your wife may not be able to qualify for foreign ownership in Thailand.
The sale contract for the condo should mention that you purchase a unit in the 49% foreign freehold ownership side of the condominium.