This is happening quite a bit at the moment, as buyers are returning. You have a legally binding lease. Chances are he won't sell quickly. If he does, the new owner will inherit your lease. If the new owner wants vacant posession, negotiate with the landlord for 3 months free rent. You should have no difficulty finding another condo.
No way should pedophilia be tolerated in any shape or form, but you need to be very careful in your choice of words. If this person discovered you called him a pedophile, you'd have serious problems. It's also worth remembering that FB is monitored by Thai and international agencies.