Maydahui 35PCS Vintage Bronze Jingle Bells (1.7 X 1.5 Inches) for Dog Doorbell & Potty Training, Housebreaking, Making Wind Chimes,Christmas Bell

Q: At a temple in Thailand, bells are hung to keep birds from roosting . Has anyone tried this with these bells?

yes,lot of people hanging these bells on tree to avoid birds roosting

Q: how wide is the hole at the top?

The diameter of the hole in the top of the bell about 0.19 inch (0.5cm).

Q: Is this material easy to drill through?

I think it would be easy to drill through, if your talking craft wise like drilling holes making patterns on the sides of the bells, I would just use an automatic center punch to make an indented mark so the bit has something to sit in. Otherwise it would be difficult and just roll around the sides of the bell never grabbing and drilling through it.