I think that the next trip you do, come to the Expats Club meeting, and ask there. I know a few people who have several properties and live off the income, and seem content.
1) Location is important, but the building very. You need a regulated one with a good management team, that keep it clean and maintain it. It may also work better if your properties are located near to each other for ease of supervision.
2) Studios, cheaper to buy and rent.
3) Success... never a guarantee there. They are building condos like crazy here, you have to wonder will the market be saturated soon. But at the moment, the Russian hoards love the warm climate and are keeping the market buoyant.
4)+5) You need to be here and learn for yourself. Don't trust your money to other people, particularly Realtors (Estate agents), who are commission driven. If your plan entails nipping over here, buying a property, renting it, then going home to earn more for another property, think again. All those I have met obviously live here full time.
I want to stress that I do not rent out property here, I feel Pattaya/ Thailand is a great place to retire, not to do business as a foreigner. For every condo you can buy in your name, there is one that can be bought in the same building, for a much cheaper price, by a Thai person, and rented out.