My girlfriend and I are driving to Bangkok soon with a couple 110cc bikes. Does anyone know anything about how easy/difficult it will be in the city to find a guesthouse that will also let us keep our bikes inside? Any specifics?
Are you worried about theft? You will be perfectly fine storing your bikes in the car park, it is not normal in BKK to store bikes inside guest houses and hotels as they all have security guards if they have a parking area. Also nobody is going to go out of there way to rob a 110cc bike, don't worry about it would be my advice
You could also try one of these hotels Thai people use to spend the afternoon with their mia noi. There is a car spot right in front of the room and a curtain so nobody can spot the vehicule number plate.
For example PB Hotel, Sukhumvit, soi 3. In the same soi there is also the Playboy but closer to the road it's noiser as many tuk tuk come and go in this soi.
Anyway as madjbs said most hotels provide security...