you can not do freelance work with a soft power DTV. Only a few visas allow you to work as remote worker in Thailand such as LTR. But this is not enforced.
💯 . I have two passeport and I used to use either when entering Thailand as a tourist but with no intention of cheating the system but they are end up asking me about my 2 passports. They take your finger prints and photos. You can not cheat the system.
I have seen many cases of guys leaving their country of application while the application was being processed. Many were successful at re-entering the country. But I think that this is a flow in their rules and it is currently being addressed and enforced.