Are you serious? If so...
1. Good knowledge of knot-Thaing is essential.
2. No conversion is required but you may need to register with TAA -suggest you ask embassy for contact details.
3. Apart from fuel, maybe a Thai partner would be useful or essential, if they don't allow foreign commercial operators. I would suggest, also, plenty of third-party insurance cover, if you can get it, from a reputable company.
4. Having a convenient airfield and good maintenance back-up are essential as the clients will be angry if you don't deliver.