100% required. If you're working in Thailand you require an appropriate visa and work permit. That some do and don't get caught is because authorities prioritize who they care about - still illegal but they mostly only really care if you're taking jobs from locals.
This interview with the CM Work Permit Office is a good summary of the general attitude.
look at the name of the group. A tourist visa electronically applied for is fair. E-visa - I'm not trying to be pedantic but understand how Thai visas are complicated to begin with. Calling something an e-visa just complicates things more.