So lets say you are a manager for a normal 9-to-5 company, and head to Thailand on vacation. If you receive a phone call from work would that technically be illegal since you are doing your paid work from a thai beach?
For a more realistic example: it is perfectly legal for a foreigner to come to Thailand on a business visa (without a work permit) for the purpose of meetings. There is even a specific 3 year (vs regular 1 year) business visa that is specifically designed for this situation (it cannot be used to get a work permit).
The "traditional" situation is evident in other things too - for a marriage visa, there is a means test ($/month income or $$ in a bank account) - the amount required is vastly more for foreign men (marrying thai women) than it is for women (marrying thai men).
In terms of a theoretical "this is intentional" answer - I don't know, because I don't actually know what the average "digital nomad" would spend large amounts of money on - I'm living basically as a resident, I haven't left the country in 9 months, we have a car, imported our dog, etc.