I transit through Dubai several times a year from London to SE Asia and back. Most of my connections are 2 - 2.5 hrs. I can't remember the last time I did 1.5hrs, but I think I have, but it was a smaller airport then.
I would say that it's doable, but you're right - it's tight. There's no guarantee which terminal you'll arrive at and depart from. B & C are connected and are walkable (but it can be a hike) whereas A is a shuttle train to connect with the others.
You have to go through transit security which can be hit or miss even in business class. I usually allow 20 minutes from getting off the plane to being through transit security and another 10-20 mins to get near to my departure gate. Emirates say you need to be at your Departure Gate no later than 45? minutes before departure but I'm sure they'll be a bit flexible with Business Class.
When connections are tight or an arriving aircraft is late they'll often have somebody at the gate marshalling the passengers for the tight connection and will call ahead and ensure they don't close the gate etc.
If you bought the whole ticket from Emirates, it'll be a legal connection - it's just on the tight end... I'm sure there will be several people travelling GLA-DXB-BKK, and you'll be one of the first off. Let the cabin crew know you have a tight connection and they'll point you in the right direction.
I think Emirates have 4 or 5 flights a day to Bangkok, some terminating there, others going on to Australia, so in the event you miss your connection, they'll get you on the next one fairly quickly. I've also sat on the ground in Dubai for half an hour waiting for connecting passengers. (But I have missed connections also despite being at the gate before the flight departed).
You obviously don't want to miss your connection but not as much as Emirates don't want you to miss your connection - they want you on that flight if at all possible. You should be fine - but go to the loo before arriving in Dubai 'cos you certainly won't have any time when you're there.