Do I need to pay taxes in Thailand on a DTV visa if I work for 180 days without a local company?

If you are a Thai tax resident and bring income into Thailand while you are you will almost certainly need to file a Thai tax return. The only income that doesn't count is usually defined in any dta between the country the income comes from and Thailand but this is usually restricted to certain types of pension.

No one here can answer that question.

If you spend 180 days in Thailand you are a Thai tax resident. Officially any money remitted to Thailand is taxable. You need to contact a tax expert to review any possible dual taxation treaties or other factors to determine if you are liable to pay taxes if you spend 180 days in Thailand in a single tax year (Jan-Dec).