am urgently looking for diamond hole saw to cut holes in glass.

Am looking for a 45mm, 65mm and 75mm model

Can anyone help me and tell me where to find those?

Assuming you're in Bangkok, I'd start around the area between Yaowarat and Hualumphong station.

You need an industrial supplier like these people:-

http://www.cromwell.co.th/

I used to deal with them in the UK in the 1970s and 80s - a very aggressive and efficient wholesaler who rapidly became one of the leading tool suppliers in the country during that time. Clearly they've expanded overseas since then. They market a lot of stuff under their own "Kennedy" brand.

Assuming you're in Bangkok, I'd start around the area between Yaowarat and Hualumphong station.

Yes you might be able to find it around Klong Tom market.