You're asking for theme, layout and decoration advice - this is difficult to give unless you tell us where it is and, crucially, who your market will be. Are you aiming at expats or tourists? Will you allow locals? Are you planning on charging for your table? What about beer prices? Ladies? - and all that entails?
I would keep the bar light, bright and airy, with good ventilation. Get a good light over the table and make it the centrepiece. A sports bar theme might work - get PL football - I don't remember too many chilled places to watch it in CM. Personal preference because of my bad back, but I always made a beeline to places that had comfy sofas.
Food - trad thai fare presumably, but i'd also go with full english breakfasts. I've been all over the world but have never had a decent full english outside the Uk. I simply don't understand why. Get the right ingredients and make sure it's cooked properly and you're onto a winner. Do not serve it with salad and make sure your cook can fry an egg properly - sack them if they can't.
In terms of pool, I'd make sure the cues were decent and there was always chalk. I lost count of the number of great chalk hunts I've had, and it's easy to forget when you've a million other things to do. I would take 100% charge of the table and playing conditions - there's no way I'd delegate any of that to a thai.
Have a winner stays on format. Encourage regulars by selling basic cues and allowing them to store them at the bar. Sell spirits by the bottle and keep them behind the bar also. Go for the Beer Lao drinkers, not the Chang alkies. Hold regular comps - both 8 ball and 9 ball - charging 100b entries. Be prepared to lose money for a few months until you build regular entrants. Maybe have an opening night comp with a prize of 10,000b, and publicise it widely.
It's a difficult sell, but perhaps not impossible. The important thing to remember here is there are a lot of players in CM, but nowhere decent to play. The tricky bit is to wean them off the snooker style tables, and that comes down to getting them to understand international rules rather than the UK or Thai rules they currently play. If they can't grasp them quickly, you've had it.
Not wanting to tell you suck eggs or anything but you MUST be a strong boss and take no shit from anyone. Staff will take the piss if they can. Keep a beady eye on everything. You also MUST talk to other farang bar owners about tea money and the like. Finally, ring-fence some emergency funds and never dip into it for the business. I take it you're active on Thaivisa? if not, get on it and talk to them about sponsorship. You'll die a slow death if you don't get yourself known.
just kidding, i'm glad to help
, kind of like Slate in NYC: 
