@Evo *******
OK. There are 2 reasons you could have been denied and you could have been denied for both of them
1. You have spent more time than was reasonable inside Thailand on visa exempt entries in the last 12 to 18 months
2. You can't legally work remotely from Thailand on a visa exempt entry
If you want to enter Thailand and legally work remotely you need to get yourself a DTV based on Workation which is a 5 year multiple entry visa that allows you to work and stay up to 180 days at a time. It's the only visa that fits your situation