Is investing/trading on a tourist visa open to interpretation?

[backpacker]

If only there was a law telling me it wasn't possible..........but so far, nobody can show me it

You will not find a law which tells you that it is not possible. The spirit of BOT/SEC is your tool to understand the reasoning of RD:
Read this -> Thailand and Cryptocurrency
in connection with my above posts #16, #18 and #20.